I recently got rid of my 40's and went to 9mm in all my handguns. I've done some hands on testing with the 147 grain 9mm hollow points vs the 180 grain .40 hollow points. The 9mm performed extremely well, with the benefit of less recoil and increased capacity. The newer heavier projectiles in 9mm are the way to go. The .357 will give you some increased zip and energy, but I don't think it is significant over the 9mm performance wise. Being that it is a target shooting gun, you'll appreciate the extra rounds of 9mm you get for the same amount of $$.

If I had to sell all my handguns and keep only 1, I'd keep my P226 SAO in 9mm.