I have been using the Snell MTB for the past year and am staying with it. Spins much better around the green than any ball at the same price level, like Bridgestone E Series, or Titleist Velocity, etc. Buying 6 dozen at under $30 per dozen makes losing one much more palatable than a $48 set of Pro V1s.
Speaking of spin, I heard a neat interview by Hank Haney with Rock Ishii, formerly the Nike ball guy, now with Callaway. Ishii said he does not use a high spinning ball because he does not spin his shots enough. That had Haney a bit confused, and he was asking Ishii why he would use a lower spin ball if he needed more spin. Ishii explained that the soft line of balls does not spin as much but comes off the face at about 1.5 degrees higher launch angle, so he can stop the ball with height instead of spin. He felt that since he did not hit chips like a pro using their ball was not a good idea. I guess it all comes down to personal feel and, in my case, price. But the Snell balls spin well and most friends of mine that try them feel it is a bit softer than the Pro V1.