Gotta say that if you get the fast twist with eye toward shooting conicals, recoil could quickly become a factor. I've launched heavy conicals from 50, 54 and 58 calibers fast enough to flatten the trajectory as I would like for longer shooting. And man.... :shocked2: They come back with as much or more enthusiasm as a heavy load in a modern 12 gauge. If you need to do long shooting past 100 yards, then by all means a conical will pay off in trajectory.
But if your shooting is inside 100 yards, a 50 cal round ball will shoot flat enough and land with plenty of authority for deer while generating a whole lot less recoil. If moose or elk are on the list I'd probably move up to a 54 cal and be happy, while still not generating objectionable recoil. Even my preferred 58 is a near-pussycat with round balls, compared to what it does at the back end with 600 grain conicals.
The round balls are also a lot cheaper to buy, and easier to make if you do your own casting.
Sift through all that, and unless you're doing long range stuff, a GPR is likely dandy. And if moose and elk aren't on the menu, then a 50 cal GPR is dandy.