Their is just one way to get to know your pistol, practice makes perfect. So if it's the G21 you like the best,That feels the best to you. Then thats the right pistol for you.If you feel you need to start out with a 9mm,Rent it for a day.And get in some practice shooting. But it come down to practicing is everything. The new G21 is a great pistol,If you read up on it.Some pro shooters feel it's the best glock ever made.