Sometimes yes, as in pointy shapes penetrate deeper than wadcutter shapes?
Or sometimes yes as in when bullet weight, shape, and length of barrel are all the same the bullet with the lighter powder charge will penetrate farther.
The only way I can see that happening is if at certain barrel lengths (which I don't think we discussed) the extra powder in the +P's is totally wasted in flash. Which IF that's the case is supportive of my original point, being; there is not that much difference between the standard and +P. I will concede that I thought there would be a slight gain with the +P and I would have to see the actual test information before I believe that's the case.