Fwiw, after my last kill @ 645 yards, using a 2.5-20 Ffp Nx8, I noticed I shot on 18x. I had plenty of time to shoot and that ended up being the power I liked for the shot. I did not think above 15x was worthless. My 4-32 Nx8 has a magically better eye box. Nothing drastic, imo, like some guys make it out to be.
The Vx5 will have better glass and be lighter weight. Trade offs with everything tho. The glass on the NX8's is adequate, especially knowing guys use SWFA scopes and kill lots of shit. Those are like putting seran wrap over the end of a paper towel roll to me.