Sorry to sound so negative, but I seriously doubt that you'd get much in the way of definitive results doing this. The problem is that these measurements are often very subjective, and most claims aren't actually measured (or all claims are measured in a different manner).
This site will give you a lot of info on range, but not groupings:
Giving this thread a quick read would probably be a good idea before getting started (especially the comments exchanged between The Bushman and greg)
As to my own personal experience, I've never recorded any groups, but I can tell you for sure that a stock TM AUG is MUCH more accurate/has more range than a stock Tippmann A5. As to upgraded performance, I've never seen the top end of paintball markers, so I can't comment.