SPUHR is known as one of the best scope mounts I know of. Really Right Stuff makes some nice tripods and now they are getting into the scope mount game. The RRS mounts look nice and are a premium price. How do the RRS mounts stack up to the SPUHR mounts?
Prior to RRS, my default mount was Spuhr. While I have purchased two RRS mounts, I have over a dozen Spuhr mounts, including cantilever versions which I use for my AR-type uppers. For evaluation, I swapped out the Spuhr mounts for RRS on my LWRC REPR .308 semi and DTA SRSA1 6.5/.308 bolt action. The LWRC has the hardest recoil in my collection (short of a 12-gauge), and the DTA system is my most accurate.
Fit and finish of the two are neck and neck. Spuhr is finished in matte, while RRS uses a more polished finish. The green bubble level of the RRS is easier for me to read than the white level of the Spuhr (though they offer a green one separately). RRS uses different torx heads for the rings and rail screws, while Spuhr uses a T-20 for both sets. Currently, RRS does not offer cantilever mounts, while Spuhr does.
In terms of retention, both mounts do an excellent job keeping a scope secured within their rings and on 1913 rails. While Spuhr uses 6 screws for each ring (for nearly all their mounts), the RRS uses 4, but both do the job well. I have found that using 15 lb-in for the rings of either system sufficiently holds all my scopes in place; Ive had problems with at least one scope when using more torque, though Ive never torqued rings so tightly that it deforms a tube. One potentially significant difference is the fact that the RRS rings are narrower than Spuhr's. This allows the RRS to fit scopes a wide turret housing or short tube sections between the objective and ocular bells.
Feature-wise, Spuhrs have multiple points on which to mount rails and accessories, while RRS has initially kept their standard offerings simple and clean. Whatever else you intend to attach to the scope mount will determine which brand meets your needs. For 99% of my use, a mount's sole purpose is to secure a scope to the rifle, and found Spuhr and RRS to work equally well.
Overall, I consider both brands as top-tier choices. RRS has not displaced Spuhr for my use, but offers an equally good alternative, and you can confidently buy either (or both). Having performed flawlessly, my RRS mounts have stayed atop my LWRC and DTA.