7mm-08, 270, 30.06 or 308.. take your pick, they all work perfectly. Really comes down to if you want to hunt something bigger some day, ammo availiblity, and cost of ammo.
270, 30.06 cheap and EVERYWHERE
7mm-08 about $10 more for 20 rounds and can't find it all the time but it's becoming more popular
308 - about $3 more per 20 than 30.06 in my area and not as previlant as 270 and 30.06 at least around my parts.