Most here know I'm pretty biased towards Leupold, but in this case, I'd put either a VX3 4.5-14X or a VX3 6.5-20X. It would depend on what you want to use the rifle for, but both are excellent varmint scopes and both can be had with 30mm tubes (LR), target, M1 or M3 turrets, choice of reticles such as the Varmint Hunter Reticle, along with crystal clear optics at all powers. Don't think the Nikon has any of these options......
I've got five VX3 6.5-20X's on various varmint rifles, and I'd not trade any of them for any other optic available right now.
This is one of them on my M21 Cooper just after removing the 3.5-10X Leupold Tactical I had on it temporarily for a squirrel shoot.

Since the photo was taken, all my VX3's have had the Leupold Alumina flip covers installed, and the rubber Butler Creek cover deep sixed..... Very cool scope covers that fold flat if wanted. Nikon does not offer anything like this either, but cost less too. Just remember: You get what you pay for (usually....).