SpockLives wrote...
Time for number crunching: AP versus Incindiary. First off, ammo powers only calculate damage based on the unmodified base damage of the gun. Those +10% damage upgrades you buy don't affect ammo powers, but +% power damage from your class passive skill does. The Vindicator is a popular gun, so I'll use it to compare these two powers.
It's worth noting that +power damage bonuses from gear or passive skills are added to the ammo power damage percentage. Thus, the 15% power damage bonus you get for wearing the Blood Dragon Armor will boost Tungsten's 70% to 85%; or Inferno's 60% to 75%. Weapon upgrades and bonuses have no effect on ammo powers (Miranda's passive has no effect, for example).
According to information gathered from parsing .ini files, the Vindicator's base damage is 36.8. So let's compare an unmodified Vindicator with Inferno (+60%) and Tungsten (+70%) ammo. First against health, then against armor (Vindicator does +25% versus armor)
Inferno versus health = 58.88
Tungsten versus health = 62.56
Inferno versus armor = 73.6
Tungsten versus armor = 78.2
So with an unmodified Vindicator, Tungsten ammo gives a noticable bonus. Now let's compare fully upgraded Vindicators (5/5 damage and assault rifle penetration).
Inferno versus health = 77.28
Tungsten versus health = 80.96
Inferno versus armor = 104.88
Tungsten versus armor = 108.56
I don't know how you got to those numbers - but this is how it works AFAIK
Vindicator base damage = 36.8 and receives a 1.25 modifier against all defenses (default). Thus, an unmodified Vindicator will inflict 36.8 dmg against health; and 36.8 * 1.25 = 46 dmg against shields, barriers, and armor.
Inferno Ammo's damage is calculated using the base damage only. This means that throughout the entire game, Inferno Ammo will add 60% of 36.8 = 22 to the total damage. An unmodified Vindi did 46 damage against armor; combined with Inferno Ammo that becomes (46+22=) 68 > that's an effective 48% increase (not 60%) in damage.
Now we add the upgrades. There are 7 AR upgrades and the bonus upgrade adds another 25% against all defenses (bonuses from passives, like Miranda's, are added to the upgrades - so with 2 AR upgrades and Miranda, you'll get an 20 + 15 = 35% total damage bonus. Basically, Miranda acts like one and a half AR upgrade). Thus a fully spec'ed Vindi inflicts 36.8 + 70% (or + 85% with Miranda) = 62.56 (68.08) damage against health; and (36.8 + 70%) * 1.5 = 93.84 against armor.
With Inferno Ammo, damage against health becomes 62.56 + 22 = 84.56 (a 35% increase)
With Inferno Ammo, damage against armor becomes 93.84 + 22 = 115.84 (a 23% increase)
At the start of ME2 and assuming one either cheats to max Inferno Ammo immediately or plays NG+, one receives a 60% damage bonus against health and a 48% damage bonus against armor. Near the end of the game (with most upgrades collected) those percentages go down to 35 and 23 % respectively (they'll drop even lower when you use weapon damage boosting gear, passives and Miranda).
The difference between Inferno and Tungsten Ammo is neglectible. We're talking about a percentage or two here, that's not something you can notice in-game. Inferno's CC effect is its most important feature (something Tungsten lacks) and therefore beats Tungsten easily. In fact, the CC effect is the only truly useful feature of Inferno Ammo (and all other ammo powers). It allows Vanguards to Charge 3 goons; shoot the one in the middle and the other two other (nearby) enemies will be doing the fire-dance

Now the numbers are much closer, percentage wise. The difference in damage to health is only 4.7%. The difference in damage to armor is a puny 3.5%. (Can any math people confirm my numbers? It's 3 AM my time.) If my sleep-deprived brain did the math right, I don't see any reason to trade crowd control for 3.5% damage.
Now let's really make it complicated. Heightened Adrenaline Rush adds +140% damage to weapons, but once again the ammo power is unaffected by this. Fully upgraded Vindicator + Heightened Adrenaline rush comparison.
Inferno versus health = 154.56
Tungsten versus health = 158.24
Inferno versus armor = 220.8
Tungsten versus armor = 224.48
Now our difference in damage to health under Adrenaline Rush is 2.3%, and against armor it is 1.66%. So, is it worth picking Armor Piercing Ammo for a class that has Incindiary ammo? I wouldn't bother. (PS, I didn't feel like checking to see what sort of bonus to weapon and power damage the Soldier's class passive gives. Someone else can do that
.)
I don't know how you got those numbers, but stuff like Cloak and ARush have no impact on the weapon-ammo damage ratio. Heightened ARush adds 140% damage to both weapons and ammo power damage; the 100% point blank range damage bonus affect both weapon and ammo damage (both are doubled but percentages remain the same).
Overall, ammo powers add little in terms of damage. Using 10 skill points to receive a 20-25% damage bonus against armor is a big investment and not worth it when there are other powers available to upgrade. It's also important to remember percentages an sich mean nothing. There is no (gameplay) difference between having to shoot 3.01 times or 3.99 times - you always have to shoot 4 bullets to kill the target. Only when the extra ammo power damage saves a shot it's worth it, which can be the case with stuff like sniper rifles - for example, but has little impact on SMGs or AR's due to their high rate of fire.