There's enough variability in physical weight of POC that you could get the same physical weight in 5/16 or 11/32 shafts. For example, the heaviest 5/16 shafts would likely be comparable in weight to light or moderate weight 11/32s. Of course, the heaviest 11/32s will be heavier than the heaviest 5/16s.
The narrower 5/16 shaft, because it rides closer to the center of the bow, also means that it might need to be spined a little heavier, say 5#. The additional 5# in spine might enable you to pick up a few more grains in physical weight as well.
The skinnier 5/16 shaft will penetrate better (ALL OTHER THINGS BEING EQUAL). Skinny shaft diameter is one of the reasons for carbon's superior penetration.
In truth, though, the differences in the two options your considering are quite small. Doesn't really make much difference on deer size critters.