My question would be "what kind of varmints?". If you mean ground squirrels or prairie dogs, then a high magnification scope would be ideal since you would be sitting in one spot and waiting for the buggers to pop up. If you are talking about coyotes, then a mid-range variable would be better so you don't miss the close-in shots. For jackrabbits or such, a mid-range variable works well because there are shots from 5 to 150 yds.
When I first started varmint shooting in CA, varmints meant ground squirrels. I started with a Weaver K4, and it worked great until I saw an ad for the then-new Leupold 6.5-20X. Suddenly, the whisper-thin crosshairs on my Weaver were not fine enough, and the magnification which had worked fine for several years was insufficient. I just had to have the Leupold, so I got one. In the meantime, I had moved to NV, and the game had changed. It was no longer sitting ground squirrels from 100 to 400 yds, now it was jacks from 5 to 150 yds at a dead run. My new sweetie turned kind of sour. I finally traded it for a Leupold 4.5-14X, and that worked fairly well, well enough that now, 35 years later, my 22-250 still wears that scope. I have used it to shoot jacks, rockchucks, ground squirrels, coyotes, and a variety of other so-called varmints, and the low to mid-power variable works quite nicely after all.