I can vouch for the reputation of the standard 6mm Remington. I've been using a Remington 700 VL chambered in 6mm Remington for 8 year's now and every summer I'm able to make clean, one shot kill's on groundhog's from 600yds, out to just a peanut over 800yds, providing the condition's are right.
There are several reason's why I personally like this cartridge. it is from my estimate inexpensive and, easy in regard's to load development.
The recoil is'nt harsh enough to prevent yourself from being able to quickly get back on target in the event that you don't have a companion spotting your shot. And finally, the trajectory may not be that of a laser beam however, with my load using 80gr nosler ballistic tip's with a muzzle velocity of 3538fps, it doe's shoot pretty flat. at this velocity, the the 80gr nosler has 362lbs of retained energy left at 1000yds, enough to dispatch a groundhog or praire dog. There are alot of .243 based cartridges to choose from. as far as wildcat's are concerned, the 6mm Remington Ackley improved is hard to beat,
the 6mm/.284 winchester can be tempermental to load for. for myself, easy has alway's been best, and that's why I enjoy the 6mm Remington so much.
Good Luck With Whatever You Choose,