All that being said, most folks just don't trust the little 6mm as much as they should. Honestly with respects to terminal performance a quality 24cal 100 grain bullet traveling 3500fps will do anything a quality 25cal 100grain bullet traveling 3500fps will do!!! I've owned a 25/06 and my boys both have 243s and with Barnes bullets in either you'd be hard pressed to notice any difference in real world effects on deer sized game. But realistically I've always felt that when most folks buy a 6mm they are doing it for 1-2 main reasons, they want 1 gun that is suitable for varmints and deer sized game and/or they are buying a big game rifle for light recoil for either women/kids or they just to enjoy smaller guns themselves. When you start hot rodding the 6mms with big cases and alot of powder you kind of start taking away their allure and if you are going to put up with more muzzle blast and recoil you might as well shoot a bigger bullet. A whitetail shot at 300yds with a 6mm bullet isn't going to be able to tell you if it came from a 243, a 6mmRem or a 240Wby.
IMHO spend some honest time with the 243 and quality bullets and you'll only grow to love it more with each passing year...
Least that's the way I see it after 20 years of selling guns in the sporting goods biz in the mid-south,
HL