I read a while through the posts in the class forum and decided to actually join the discussions because I think it's kind of interesting how to spec stuff.
I looked deeply at the skill trees of the mage. Currently I am at level 10 at don't have the option to learn a specialization. Didn't played the Skyhold Mission yet. I spend a lot of time in the Hinterlands and did almost every quest there. I finished the mission where the undead's come out of the water.
Currently I'm running a mage that has abilities in Spirit, Fire, Storm, Winter
1. Barrier
2. Peaceful Aura
3. Complete left side of storm tree (which was kind of a waste, but at the moment it works fine)
4. Flashfire (was the starting skill, wouldn't take it myself)
5. Immolate
6. Fade Step
7. Mana Surge
So I cannot decide if to go with KE or Rift Mage but I kind of agree with @Ishten. KE is nice, we don't need to discuss that, but it's close combat and like Ishten I like to be in the distance. Personally I think a mage is a supporter or damage dealer from the distance. In most games that is the fact. If I want to play melee I would choose Warrior or Rogue.
Besides that the Rift Mage tree looks interesting and has nice abilities. I like the Firestorm AOE just because it looks cool and the Abyss is nice too. The bad thing of the Abyss in my opinion is that it takes a while until all enemies get sucked to the mid point. I think Static Cage incl. its upgrade is just doing a nicer job. Keeps crowd in a defined area, deals additional damage when you or your allies deals damage.
Well the synergies are kind of interesting here. Static Cage + Chain Lightning + Immolate + Energy Barrage (eventually). The question is if you can cast all this in 8 seconds because of the cool down times. If you also have clean burn I guess you don't have any troubles with Mana regen and cool down.
So as you see you can have a very versatile mage. Winter's Grasp is another option. Just depends a lil bit if you want to slightly balance in the direction of damage or crowd control. Personally I only really like Fire Storm from the Rift tree because it's kind of cool. Other abilities could be exchanged with more interesting ones in the standard trees.
Still don't know which one to go but I currently experiment until I got a specilization and will then respec. KE is still veeery attractive but there are a lot of people that extremely liked it at the beginning and then were totally bored because it a.) always the same combos without the need of good timing and b.) it's just to easy and you don't really need to synergize with the rest of your group. Personally I like to have Solas in the group with Rejuvenating Barrier, Revival and Dispel. You can really build up a heavy group. You + Solas (focusing on Spirit, Winter) + Heavy Tank + Archer/Second Tank/Assasin.
My 2 cents. Still, not commited to either Rift/KE or Basic Trees but for Singleplayer I tend to basic trees. For Multiplayer I guess Archer or KE is just much fun 