I had a G20 once & sold it due to ammo cost...$16.50 for UMC stuff !!...Thats crazy...I think most people are more accurate with a 9mm & a 45 vs the 40...I guess If you buy the gun that feels the best in your hands & the caliber that you are most accurate with...you really cant go wrong...Try before you buy...
I wouldn't use +P ammo in a G30 or G36... you'll just get more muzzle flash, noise, recoil, and slower follow-up shots, and not much more velocity out of those short barrels.