RE: .243 for whitetails
It's usually best to shoot the biggest rifle you can shoot accurately without flinching, but you first have to find out what your limit is, and that's tricky, especially if you haven't fired a large variety of rifles and shotguns in the past.
So, I would recommend the 7mm-08, or the .308.
The 7mm-08, as previously mentioned, is pretty much the .243's bigger brother, and therecoil isn't much moreat all from what I hear, but the performance is definately better, since the 7mm-08, like the .308, at close range (up to 250 yards), is considered eithical, and sufficient for elk, whereas the .243 isn't.
The problem is that 7mm-08's aren't so common.....yet, the average round I belive is a 140-grain, which is more than the .243's 100-grain, but the recoil is just a little bitmore.
If recoil does end up bothering you, go to your local gun store, and get a Limbsaver, my Grandpa put one on his 30-06, and it now kicks less than my .308which hasthe factoryrecoil pad.
I'm sure if you applied one of those toa .308, is would kick for sure like the .243, ifnot less.
Like Rifleman said,there is noonerifle or cartridge foreverything, and manysmart people on here could tell you that the best rifle is the onethat fits you, and the oneyou're comfortable with.