Another opinion in the pot; any of the mentioned calibers would be effective. Personally I would start with the .270 but; I would pay more attention to the rifle you plan on purchasing than the exact caliber. If you are recoil sensative I would not purchase a feather weight rifle, the percieved recoil is greater in a light rifle. It would be worth the extra pound and a half carry weight. Stick with a rifle that is at least 7 lbs or more, I wouldn't go over 9 lbs however if you do much walking. There are several factory rifles sold with excellent decelerator pads installed, they do work. I agree with UncleNorby with the caliber selection, start around the 260, 7mm-8, 25-06, 270, you would have a hard time telling the differance between any of these in measured recoil. 30-06 can be a little rattling for the recoil sensative esp. in a light rifle. 270 is the second most popular caliber ammo sold during deer season in the US only second to the 30-06, I don't think that many people can be wrong.

If you have money to toss around there are a few companies out there that claim their stock recoil system along with a compensator can tame a 270 to recoil like a .223.