For GSSF indoor league I think you'll be fine with the Performer line. Yes the trainer pistol will be physically lighter (and less expensive) than the metal version, but I think paying the premium for the extra weight wouldn't necessarily be worth it.
For action sports like IDPA/USPSA or even outdoor GSSF, you might want to have the weight be as close as possible to your competition gun. That way the swing weight will be similar.
Full disclosure, though, I have the Pro version but I bought it before they released the less expensive version.