The Darkspawn & The White Walkers (otherwise known as the Others)
This comparison will draw from the Dragon Age Wikipedia and from the A Song of Ice and Fire as well as Game of Thrones Wikipedia. If you notice anything you consider a mistake, feel free and unguilty to ask for correction. This will contain spoilers from the fifth season of the HBO's adaptation "Game of Thrones". The sections containing spoilers are: Origin, Leadership and Vulnerabilities & Strengths.
Name
The white walkers are referred to as such by wildlings otherwise known as the free folk but are known as the Others to those south of the Wall.
The darkspawn are referred to as such by most of Thedas though individual languages may have their own name for them as among the Avvar they were known as night-gangers.
Origin
The white walkers have no known and confirmed origin but there are those who attribute them certain origins and allegiances.
According to Melisandre of Assai, the Others are servants of a deity called the Great Other, who is the god of darkness, ice and death. This Great Other is locked in eternal warfare with R'hllor, the of of light, fire and life.
According to legend, the Night's King was a legendary commander of the Night's Watch who lived during the Age of Heroes. He was the thirteenth Lord Commander and considered to be fearless. He fell in love with a woman "with skin as white as the moon and eyes like blue stars". He chased her and it is said that as he gave her his seed, he gave her his soul as well. He brought her back the Nightfort and declared himself king and her his queen, ruling the Nightfort as his Castle for thirteen years. Horrific atrocities were said to have taken place and after his fall, it was discovered he had been making sacrifices to the Others. Because of her appearance, som fan theories has linked the Night's Queen to the white walkers because of her appearance and a recent appearance in the television episode "Hardhome" as well as a leaked name has lend credence to the Night's King connection to the White Walkers.
According to legend, the Others first appear during the time in which peace reigned in Westeros due to the Pact between the Children of the Forest and the First Men. Because of this, they were unprepared for the scale of the invasion. It is said that the Others' arrival were preceded by a Winter that lasted a generation and a period of darkness known as the Long Night, although it is unclear if this is a literal period of darkness lasting years or merely an artistic term. The Others' ability to resurrect the dead as wrights made them nearly unbeatable but after a long and grueling war, they were pushed back and salvation finally came in the discovery of obsidian which could slay the Others. In the War for Dawn, Azor Azhai wielding a sword of fire called Lightbringer led a crusade that turned back the Others and banished them into the uttermost North. Brandon Stark then built a huge wall of ice to prevent the Others from coming south again aided by the Children of the Forest who made it so that the Others could not leave the north by passing the Wall. It is said, however, that their wrights can. This origin has the white walkers appearing from nowhere to cause devastation upon man.
The darkspawn have no fully known and confirmed origin but it appears some of the origin attributed them by the Chantry has some credence as an ancient, sapient darkspawn emissary named Corypheus was discovered by Hawke and his companions. Corypheus claimed he was a magister of the ancient Tevinter Imperium who, with an unspecificed number of other magisters entered the mythical Golden City only to find it black and devoid of the Maker they were expecting to find. Some of his comments of piercing the heavens could be used to lend credence to the interpretation that their attempt involved entering the Fade while awake, thereby piercing the veil and bringing themselves physically into the world of spirits and dreams where a floating black city is sometimes observed to be. His references to Dumat in his initial introduction may suggest their attempt were influenced by an outside force.
According to the Chantry, the darkspawn were created when the magisters of the Tevinter Imperium opened a portal into the Golden City, tainting the realm of the Maker with their corruption and returning as the first darkspawn, their evil transfiguring them into the monsters they became. The First Blight begun as a result of the magisters growing in numbers and digging Down into the earth until they became upon the resting place of the Old God Dumat believed to have been imprisoned there. Freed from his prison and warped by the taint, Dumat became the first Archdemon and began the First Blight. The Chantry thusly believe that it was the hubris of man that caused the creation of the darkspawn.
According to the dwarves, the darkspawn simply appeared underground and their invasion of the Deep Roads ended up crippling the once great dwarven empire, leaving only Orzammar and Kal'Sharok, the latter of which became completely isolated from the outside world for a long period.
According to the magisters of the Tevinter Imperium, they deny that any ancient citizens holding the title of magister were involved in starting the first Blight. They claim the darkspawn have always existed and the magisters have no connection to them.
Leadership
The white walkers is led by a white walker known as the Night's King who was once the 13th Lord Commander of the Night's Watch. Beyond gathering and leading his army south, his end goal and motivations are unknown.
The darkspawn are led by a darkspawn known as an Archdemon. Each of these Archdemons are believed to have once been one of the Old Gods of Tevinter until freed and corrupted by the darkspawn in its underground prison that lies somewhere in the Deep Roads. Beyond uniting the darkspawn through the use of it's blight-calling referred to as the song and marching its armies upward towards the surface, its end goal and motivations are unknown.
Intelligence
The white walkers display an intelligence at the very least equal to that of a man while their wrights are said to have rudimentary intelligence. With Hardhome in mind, the white walkers seem to have a grasp of psychological warfare and an ability coordinate on a larger scale as well as have their wrights employ stealth tactics. They seem to be able to construct buildings of larger as seen with their ice fortress and construct weaponry as seen with their blades.
The darkspawn display a very limited intellience and seem to lack a sense of coordination without the addition of an Archdemon to their hivemind. The average darkspawn is said to possesses no intelligence beyond that of a simple animal's cunning and most are unable to communicate in anything but roars and grunts. Archdemons, emissaries as well as hurlock vanguards are able to communicate albeit more to each other than in any language comprehensible to non-darkspawn. Some veterans of the Grey Wardens, however, claim to be able to understand parts of the Archdemon's speech in their dreams.
They seem to rely primarily on numbers to the difference in combat.They seem to lack the focus or ability to build homes, instead they seem to be only able to construct primitive armour, weaponry and fortifications. They seem to scavenge as well. Without an Archdemon, the darkspawn's focus is primarily on expanding the horde and killing those they do not convert.
The Archdemons possess an intelligence far beyond the average dragon and is able to coordinate the otherwise chaotic darkspawn into a vast army capable of threatening kingdoms by using the hive-mind. It is able to do this even if it is not in the presence of the darkspawn it is commanding. It is supposed by some that the transformation into an Archdemon, drives the Old God mad though others believe beings such as it is beyond understanding.
"Reproduction" & Reproduction
The white walkers can transform the living into white walkers and the dead into wrights. This applies to animals as well and they appear able to control the animals as they do humanoids. They do not appear to be able to reproduce.
The darkspawn can turn the living into darkspawn but cannot affect the dead. This applies to animals as well though they do appear to be able to control tainted animals. They are able to reproduce by taking female members of different races and force them to undergo a procedure involving repeated "violations", taint exposure and forced cannibalism until they become a special kind of darkspawn known as a broodmother which is able to birth darkspawns.
Appearance
The white walkers have the appearance of tall, slim humanoid with cold blue eyes and chalk white skin. They wear reflective armor and wield, thin crystal swords. The wights have a corpse-like appearance but shared the characteristic of cold blue eyes.
The darkspawn have the appearance of mutated humanoids with ghoulish features like exposed teeth. Their appearance overal differs between the different types of darkspawn with ogres surpassing the kossith in terms of the size of their bodies and horns and shrieks becoming slimmer with more elongated faces. Their skin varies from genlock to shriek with some being an type of yellow to others being a type of grey. Darkspawn appear to have no hair regardless of which race they originally were. The Archdemon have the appearance of a high dragon albeit a far more skeletal version which hides appear to be a dark shade of purple.
Vulnerabilities & Strengths
The white walkers are impervious to damage from any weapon or material not of obsidian or valyrian steel. Any blow from either "dragonglass" or "dragonsteel" causes the white walkers to melt into ice water. The effect appears immediate. They are believed to be vulnerable to extremely hot fire such as that breathed by dragons and possibly to daylight but both of these, however likely, are currently unconfirmed. At least one white Walker, known as the Night's King, seems to be capable of magic as demonstrated when he used it to seemingly turn a living infant into a white walker and later when he raised the dead of Hardhome into wrights.
The darkspawn are pervious to damage from any weapon or material. Some darkspawn seem to be capable of some sorts of magic. which is due to the darkspawn taint also carrying magical power equivalent to lyrium allowing darkspawn units known as emissaries to cast spells even those who appear to have once been dwarves. The magic is believed to be unique and referred to as "blight magic".
The world's perception
The white walkers are considered to be folk figures from stories and nothing more by most of Westeros with the exception of some in the Night's Watch and the free folk.
The darkspawn are considered to be a real and legitimate threat by most of Thedas especially to the remaining dwarven kingdom who are in constant battle with them to keep and reclaim territory.