RE: Difference?
The 7mm ultra mag is just more powder and thus more velocity (about 250 fps more with 140 grain bullet). Not worth it in my opinion. If the 7mm Rem mag isn't enough then go up in caliber (300 Win mag or 338 Win mag). Not to mention that the ammo for the ultra mag will be hard to find (unless you plan on handloading). Just my .02