Sorry to repeat what's been said before, but people seem to be disagreeing alot. I'm wondering what ammo power to use. Going to create a vanguard and play on insanity soon, did a trial run on Purgatory insanity today, wasn't that terribly hard really (though I died a lot before remembering that melee now has it's own key) and very exciting. Normally I would leave ammo powers to squad, but since I'm running with Samara and Miranda I'll have to do it myself. The idea I have of the different ammo types is:
Incendiary Ammo: Imbues your attacks with a powerful DoT which is highly effective against armor and health, and causes organics to stumble in fear when armor is stripped away. Also stops regen. Do the DoT stack if you shoot several times before the duration is over? Doesn't seem very good for vanguard since target often dies very quckly before the full potential has passed.
Cryo Ammo: Freezes targets when only health is left. Seems useless for the vanguard except for squad, since loads of targets die on the first hit to health anyways.
Armor Piercing Ammo: Equally powerful or more powerful than Incendiary, and works against the same types of defense, but delivers the bonus instantly rather than after a DoT. A decent, no-nonsense buff for a vanguard.
Shredder Ammo: Only works against health, but also gives the highest buff of any ammo power. Does it stop regen? Again, seems pretty useless against anything but vorcha and krogan, since most targets where health is a major defense are very squishy anyways.
Warp Ammo: Works against barriers, armor, health and targets affected by slam, pull and singularity, everything except shields, but also delivers the lowest buff of all. Seems the best along with AP.
Disruptor Ammo: Very strong against shields and mechs, but can't be gotten without Zaed so pretty situational.
In addition, I'm wondering how I should evolve my ammo if I get AP, Warp, Shredder or Incendiary. Samara and Miranda won't get anything since I won't invest in two ammo powers if I get Tungsten/Heavy Warp or Inferno for example, but will my own bonus outperform the boost Miranda and Samara would get from say squad AP instead of Tungsten? Also, I'm curious do Shredder, Warp and AP have any visible effect like the fire from Incendiary or the freeze from Cryo? I guess the bonus ammo powers are slightly reduced by the fact that picking them means no reave/barrier.