I was always told to get a bullet that will hit like a truck, but still exit out the otherside. This means, according to what I was told, a +P+ carried too much velocity, would not create a large enough cavity while exiting. However, a +P, while fast, would be slow enough to create a nice sized cavity using a 9m and still be able to exit. (Assuming we're talking about the same sized slug of whatever configuration for comparison.)
Again, this is just what I've been told. I haven't been experimenting on any heads...
