Yes, the ammo expense is the issue. Not so much for matches as handgun stages are usually few and low round count. It's the training where I would feel it most. On the plus side there are often longer distance pistol shots, some out to 50-60 yards. A red dot equipped 5.7 would ring the steel just as well as a 9mm/.38 super.

My largish hands don't mind the longer grip of the current 5.7 pistols. Currently I favor the S&W 5.7 pistol.