First off, the two applications may seem similar to non-hunters, but IME varmint hunters typically max out at around 16X or so, and target shooters usually start at around 16X for scopes and go up from there. The reason is that even if you are shooting ground squirrels, there is no need for that much magnification, in fact it usually gets to be a problem becasue animals move and holding a rifle steady with that much magnification is a challenge. Target shooters, on the other hand, shoot from steady benches with adjustable rests, and their targets do not pop up at varying ranges or suddenly jump up and run 25 yards off to one side. So, like I said, different applications.
That said, I have a Leupold 4.5-14X VX III on my 22-250. I started out with a 4X with fine crosshairs (it worked just fine out to about 400 yds or so), switched to a Leupold 6.5-20X, then stepped down a notch to the 4.5-14X. Too much magnification is hard to use in the field, you can't find animals up close in the narrow FOV, and if they move you've got to go looking for them all over again.