Fair question, I have a Leupold on there now and it seems to randomly shift zero once in a while. Also, reading on other forums a lot of people claim Leupold don't track consistently when dialing. I mostly just want to try something different.
I'd prefer a Pre-'03 Vari-X series to anything in the VX -1, 2, 3, II, III, or 3i if I were needing to dial, IMO the pre-03's were a better made scope, they were still stamped "Made In America" rather than "Assembled In America".
Regarding the OP, Nightforce is an easy decision for me over Vortex. Vortex changes their line often which significantly devalues each earlier generation of scope.
Someone better versed in Vortex warrantee will have to comment regarding the line-up changes and what happens when Vortex no longer makes the scope you bought with OTC replacement warrantee? Do they replace with the newest model or are you on the hook for some $$ for the new one?