IMO only,
US Optics SN-3, 3.2-17x44mm, reticle and knob clicks of your choice. If you and your rifle can shoot to 1800 yards, this scope can. The optical clarity of the SN-3 is pretty clearly superior to the Leupold or NF. (I haven't compared it side by side to the SB yet.) Note that the USO scopes are very heavy.
My two serious bolt rifles are getting a pair of SN-3's ordered for them this week:
1. For the AI-AWP in 308 (and later 260REM), a 3.2-17x44mm SN-3, 35mm tube, 0.1mil click EREK knob, and the Horus H25 reticle.
2. For the 50BMG, a 3.7-22x44mm SN-3, same rest except the mil-scale reticle.
If you are serious about a USO scope, you have until March 11th to get in on the SnipersHide group buy.
-z