Thanks you for the informative replyI own both and 3 of each. I think the SIII may edge out the STAC glass a bit but so little that when and where I use it really doesn't matter. I hunt with mine. Shooting beyond 1000 yards at varmints and steel doesn't seem to make a difference. Mirage effects both scopes as it does all. Clarity and quality is excellent on both models. Deer at up to 700/800 yards max doesn't seem to really favor either scope. I'd say if there are some competitive shooters out there using both, they could give you more input on targets. I don't think the STAC is designed for use in competition IMO. Personally more of a tactical/ hunting scope.
Anytime. PM me if your interested in shooting a few. We live in the same state. Gladwin county is my home county. Gladly let you check out a decent selection of Sightrons.Thanks you for the informative reply