I have several of both the 2.5-10x42 and 3-10x42. I see no difference in optical quality. I haven't experienced any difference mechanically whether dialing or upon initial sight in.
The NXS has a red or green (easily changed by holding down the "on" button) illuminated reticle.
The NXS models I have are equipped w/exposed turrets and zero stop
The NXS has 20MOA/spin vs. the SHV's 10MOA/spin.
I hunt them interchangeably. In the open country I hunt the Illum reticle is a non-issue. The zero stop is handy as is the 20MOA/spin but none of those are deal makers/breakers for me.
