Anything from .243 to the .30 caliber (non-magnums) will do fine! Magnums are just not needed for Whitetail, and the 30-30 is OK if you don't stretch the range. The .243 will take any Whitetail with the right bullets, out to 250-300 yards. If you want a little more gun, keeping the recoil light, the .260, 25-06or 7MM-08 will be hard to beat! The .270, .280,.308 and 30-06 will do it all.... and more!
Personally, I like the .308 and it's offsprings, (.243 and 7MM-08) the best!