Ok so here the deal... im going back and forth on this.. which is better? same points.. but advantages and disadvantages to both.. Ideas?

I go with autocannon..... hasn't really done much for me, but neither has the heavy bolter when I've used it, so I went with what I use the most.

Two have very different roles.. what do you need to do? Hunt enemy APCs? Bottleneck some Orks? Brush wounds off of Monsterous Creatures?

..bring the right weapon for what your army needs and your good

im really looking for the best all around weapon... I have only one choice left for my list... i can take either hbolt or autocannon... and i need both.. i need trop killin and tank hinting...

By and large, I prefer heavy bolters. They're useful against just about any infantry, and will wound T3 models on a 2+ just like autocannons. Autocannons have a bit more specialized role against light vehicles and lightly armored Monstrous Creatures, if your enemy isn't packing such targets the lower rate of fire will hurt you.

What I'v always done in this situation is take two examples of common targets I expect to be shooting at, thats usually a space marine stat line and like a orc stat line and simply compare the numbers needed to achieve wounds.

I haven't played in a while so I can't give you examples but I have always looked at different choices in the game by the numbers, after all thats what its actually about.

So you just average the dice rolls needed to achieve a wound, the gun with the lowest total wins, of course you have to account for multiple shots but thats pretty easy.

My point is you should try looking at the numbers.