Re: 7mm Dakota
I think Lens' answer was spot on. Since (i'm guessing here) you'll be reloading, you can get the most from each chambering. All can be down-loaded a bit, but you may find the 7mm REM to be accomplish most of what the others can do in a more efficient package.
BergerBoy - "The mind works best when open..... Kinda like a parachute. "