Well, the 2910 has a better power to weight ratio, so on slopes it'll be a better climber. The 3010 has a lot of extra mass, so is much better for heavy work. Since I log (and now dig) with mine, I opted for the 3010.
There was a really good summary of the differences between the two machines somewhere...I think it was on Steve Carver's site. In fact, I'm sure of it. Browse around his informational pages and you'll find it.
Be sure to tell us if you made the right choice!
Pete