My 0.02 - Mec-Gar makes very reliable mags, some come with anti friction coating making them smoother.
Whatever you practice - practice with the mags you are gonna use and make sure you know very well how much ammo you have in the mag/s.
Sometimes you don't wanna go dry before mag change but dropping a 19rds mag after shooting 15rds is a (5rds!!) waist.