What have you compared the Sightron to?
I've currently got several Bushnell ETs (6-24x50 FFP, DMR, XRS) but used an S&B for a few months and a friend's Viper PST 6-24x50.
Here's a post from the "truth about Leupold" thread
"Regarding the value issue: The Mark 4 that I owned sells for $1100 new, for a SFP 3.5-10x40 scope with side parallax, turrets, a fairly basic but glass etched reticle, and nothing else.
In comparison:
1) Sightron SIII 3.5-10x44 mil/mil scope. Sells for $650. Very comparable to the Mark 4, but made in Japan, has better glass to my eyes, slightly better turrets, slightly larger objective and therefore exit pupil, and doesn't lag behind in anything I can see. This is the most direct comparison I see to the model I had, and it costs less than 2/3 as much for a better scope.
2) Burris MTAC 3.5-10x42 mil/mil scope. Sells for $400. It is in a lower tier and may not have the same durability as the Mark 4, and the turrets are not as nice. It still has a focus (but objective) and glass clarity is surprisingly good for its price. It also has a second generation mildot with the half-mil ticks, which I like (and it's also a glass-etched reticle). For training use this would be comparable, though admittedly I would not compare it for duty use.
3) SWFA SS 3-9x42 mil/mil scope. $600. Slightly lower magnification and no focus, but FFP reticle with a nice modernized reticle, very rugged, glass is maybe a tiny bit behind the Mark 4, maybe not.
4) Bushnell Elite Tactical 3-12x44 FFP mil/mil. $900. Broader magnification range, equal or better glass clarity, FFP reticle with G2 tree reticle option. It does more than the SFP Mark 4 for $200 less, with no drawbacks I can see."
-SomeOtherGuy
So SOG above rates the Sightron glass better than the Mark 4, the Bushnell ET312 and the SWFA.
Joe