I use a 7mm remington mag for deer and elk hunting. It'll outshoot me. Unless you're hunting pronghorn in wide open country where a 400 yard shot might be the best you get, you really don't need the extra oomph from the super. The 7mm has a better BC by bullet weight compared to the 30s, so it'll stay in the kill zone at longer ranges. I've heard the super will outdo the Weatherby by a fraction. It's still more than I need either way. If I were gonna switch, I might go to the short magnums that are coming out. They say you get the same performance with a little milder recoil. The 7mm mag don't recoil as much as the 300, but it will slap ya a little bit. I read last night that the 7mm super with a 140 grain bullet will have a MV of 3,500 fps. That is long range varmint hunting speed for a deer round. I guess that'd be a good character for pronghorn.
Personally, I won't take a shot past 300 yards or so at game. I've got a sweet setup (browning A-bolt stainless with BOSS comp and Leupold Vari X II 3-9x40), and it'll ring the gong at 400 yards, but that's at the shooting range.