I use and like both, and I'd really hate to be shot by either.

To me, bullet type and construction matter a great deal.

Right now, if I want solids, I'll go with the 45 auto. I really like a lot of the hardcast and FMJ choices out there. Hard hitting with decent penetration, especially from a modern 45.

If I want JHP's I'll go with 40 S&W. I really like how XTP's perform at 40 S&W velocities. These are my choice for go to carry.

If I want lead free HPs, I'll go with the 45 or go up to 10mm auto. I can't get the lead free 40's to do as well as I'd like at the S&W velocities. Bumped up just a bit, they can be pretty good. The 10mm lite loadings with some of the lead free options are nice.

Just my thoughts from seeing how the available choices work in my guns and on the things I shoot.