It is worth considering what area you are hunting in. If noise is an issue, it is hard to beat the triple-deuce. I've got a Rem. 788 with a Bushnell 4200 6-24x and it'll drive tacks with 50gr. VMax's. It was quite effective to about 250 yards (max.) but I had to make sure I hit them 'hogs very well beyond about 175. The nice thing is, I'd be only 100 yards from my in-laws place and people in the house wouldn't hear the shots.
When I could shoot a louder gun, I used a .243. That tipped them over, as far as I could hit them (and probably further /ubbthreads/images/graemlins/smile.gif ) .
That covers what I used to use, because that's what I had. When I can get after hogs again, I'll certainly keep using my .222 - I love it! If noise were not an issue, and shots were never over 400 yards, I'd probably vote for an accurate .22-250. Beyond 400 yards, something in 6mm cal. would be a better choice for reliable kills.
I own a .204 now and am looking forward to trying it on groundhogs. I haven't mentioned it, only because I have no experience with it yet.