I own both, Sightron SIII 8-32X56 MOA-2 and a Viper PST 6-24X50 EBR-Mrad and I'm trading mi sightron for a second viper PST.
Glass may be a little better on the sightron, at least that's what a lot of people say on every forum I've checked. To my eyes "my" scopes seem very very close, can't...