Jero has mentioned in a thread that "one of them has more bass", but I'm not sure where he read that.
Probably gonna get one of these... but I see a new V.2 on eBay from a dealer, and I'm assuming what you'd normally get now with a new one would be V.3.
Yea, I don't know. The person I got mine from said they thought v1's had more bass, but I have no idea if that's true. I have only used this one, and it does hold up nicely there...no idea if later ver. would be any diff.