The RAZR2 has a much more aggressive tread pattern. I guess if you need the extra side bite it wold be worth the money. I have found the regular RAZR offers plenty of traction even in the muddiest, nastiest garbage I have thrown at it. I have followed right behind 4x4's going into mud where my front tires were nearly disappeared and have pulled myself through.
I think that most of the guys that swapped out their rubber once the Razr was available for the XX went Razr 2 in the front and Razr on the rears. That is what I have and I would go that route again. The Razr 2 will corner that pig a lot better. I'd pay the difference for the 2's myself.