For that matter, there is a huge difference in white-tail themselves. One in say, Alabama doesn't hold a candle to say the big boys of Saskatchewan. I have hunted white-tail a lot in PA and plenty of muelys in Utah. I see no difference in body size between the white tail I have hunted in NW PA and the mule deer in Utah. (antlers is something totally different) A few of my hunting friend prefer a 243 for mule deer. The carry Remington model 7's in this caliber. Nice and light rifle with no real noticeable recoil.
I just find it funny when people think a 300 RUM is necessary for deer. Plenty of deer are killed every year with 22 cal center-fires.
I'm not poking at anyone, just throwing my experiences out there.