I use a heavy barrel varmit rifle in .308, 2 lb trigger, glass bedded, and some really good glass on top. I'd never hunt prairie dogs with it, but if you want reach way out and touch a groundhog or coyote, it's just the ticket. True, it has a rainbow trajectory compared to some of the .22's out there, but at extreme range it hits the same place repeatedly. And, it's bringing a load with it when it gets there. I love mine.
My advice: whichever rifle you can hit with, buy.