How many times have heard of people surviving all sorts of seemingly fatal shots? Headshots, lung shots, etc. The issue isn't will bullets kill bigger, stronger guys. They will. Bullets can kill everyone. Thats why they're the equalizer. But the question is are larger people effected, in any degree, less than smaller people.
I would say yes. I don't want to be accused of being some sort of internet tough guy or anything, but I may be coming from a different (and equally biased) point of view, as I'm a larger guy. 5'8, 235lbs, bench 325lbs and, if I remember the last measurement, had a chest that was like 48inches. And in my martial arts experience, guys who are bigger and, importantly, harder (muscle density) can absorb more and stronger punches and kicks. Muscle density also contributes to less shock and energy dispersion through the body. A tightly clenched stomach will feel localized pain, an unclenched stomach will allow more of the force to ripple through the body.
Harry Houdini (in great shape) was killed by a punch to an unclenched stomach that contributed to a ruptured appendix. Not dying immediately, he allowed the same person to punch his then clenched (muscle density increased) stomach, and didn't even flinch.
Also bear in mind that larger people have different shapes. They may have larger torsos covered in more muscle, but their organs are still about the same size. Especially in people who have muscle on the frame, it may just be harder to identify/hit vitals. You might assume you're placing good shots, but really missing the targets.
Continuing, there is plain and simple more tissue to travel through. So a lot of things will come into play involving the bullet and velocity. An extremely obese person might be better off as they'll have several more inches of fatty tissue to protect them before the vitals are in danger. However, they may be more apt to feel shock patterns and suffer internal disruption from the impact, as fat is easily moved. One really effective I found in fighting overweight opponents in the ring was to kick up at their bellies and hit the fatty overhang, which they said was very painful as it sent the force waves through them rather than letting the muscles under the fat absorb the hit.
So in my opinion I think someone who is DENSER will have a MEASURABLY different tissue damage from a bullet.
This in no way means they are bullet proof, nor does it necessarily imply a greater survival rate, though that could be the case for some wounds.
If you took a skinny guy, a fat guy, and a body builder, and shot them all in the same place with the same round, I wouldn't be surprised to see each of them have a different wound, with the degrees of severity being at least somewhat favorable to the larger guys.