I found this thread on swtor.com and thought it was pretty interesting and had some cool information.

http://www.swtor.com/community/showthread.php?t=587930

Heat versus ammo is something I have been hearing since beta and I'm wondering if any of you have found information outside of that thread before that confirms heat is better or equal to ammo? If the author of the thread is correct, the difference is marginal, but enough to mean the difference between regeneration levels.

EDIT: Also interesting. http://www.swtor.com/community/showthread.php?p=5756657

Their kind of true, but ammo is a bit 'behind the scenes' thing, and even if the game is telling you that the attack dropped you to rank 3 regen, it will jump up to rank 4 before GDC is over, resulting in 0 or very tiny difference. The MH/OH is more of an issues as Snipers/Slingers. And I seriously doubt the 14 Pulses/48 Bursts thing under same conditions.

There are tons of these little things, Like Guardian/Juggernaut DoTs one is a bleed the other is a burn, meaning that Assault VGs are better off with a Guardian in the mix that a Pyrotech and a Juggernaut.

Derpy wrote:

Their kind of true, but ammo is a bit 'behind the scenes' thing, and even if the game is telling you that the attack dropped you to rank 3 regen, it will jump up to rank 4 before GDC is over, resulting in 0 or very tiny difference. The MH/OH is more of an issues as Snipers/Slingers. And I seriously doubt the 14 Pulses/48 Bursts thing under same conditions.

I figured a difference wouldn't effect it much, maybe over 10 minutes of timed Ion Pulses/Flame Bursts, but I don't think any boss fight is designed like that. The MH/OH issue for Merc Vs. Commandos doesn't seem like that big of a deal, and there is been plenty of testing of the Sniper/Slinger issue. As one reply said in my initial link, any accuracy over 100% favors the Gunslinger as the OH hits far more often resulting in a combined higher damage. However, this is if both parties are geared and spec'd identically, I'm not sure how this would change if the gear was itemized differently from Sniper to Slinger.