I'll agree with all that's been said. It's really all about application and personal preference in the end. Either way, you'll have to know your target and what's beyond it. The velocity difference isn't enough to make one caliber safer than another.
"Better Performance" imho is a subjective term. I've hunted for about the last ten years with a 708, my hunting partner hunts with a 7mag. We hunt Whitetail and hogs. I'd bet no animal shot by either of us could have told you there was a difference between the two rounds. Very few tracking jobs for either rifle. Sure, the mag is a little flatter shooting, and it will hunk a heavier bullet a little farther and flatter (it's intended purpose). But any shot 300yds and under, there never was enough difference to make me want the larger version.
I did pick up a 280 imp this year, in an Encore. It is dedicated to be my heavy(er) bullet rifle. Shooting 160 bullets primarily. And it seems to be performing just fine thus far. But again, I bet no animal I've shot with it so far could tell you there's a difference between it and my 708. Not even the Elk I flat missed this year, LOL.
One caliber, the mag, will be a good bit louder, have much more recoil, and burn a lot more powder.
The other, the 708, will benefit from less powder, lower recoil,, and a reduced amount of noise (although still a high power rifle).
Then there's always the 280 rem. It falls out in between the two rounds being discussed here. Just food for thought.
Like stated above, you already have the brass and some components. That might play in to your decision making. It might weigh heavily on mine. But if the 708 is something you feel you need or want, I don't think you'd be disappointed. It is quickly being adopted by an ever-growing number of hunters here in the south. And I don't think I've ever heard of anyone who got one and found a real deficiency with it when they used it within it's limits.
