I think that what the pros do for practice and what us mere mortals need to do may very well be different.
Practice your weaknesses.
I bet I have much different weaknesses than Angus, Matt, Robbie, etc.
Right now I know I need to work on my target-to-target transitions, and mostly my shot calling. I think a .22 will work just fine for those.
If I were practicing for American Hangunner, I think I would need to shoot plate racks with my regular gun and regular loads, the timing and gun cycling would be just way too different.
Then again there is much practice you can do without firing a single shot: dryfire, reloading, drawing, stepping into/out of shooting positions, sight aquisition through ports, physical conditioning, etc.