Having flown both, I'd say that the airframe improvements are significant enough that I'd definitely go with all of the changes there.
Did I notice a lot of difference in the engine? As a pilot - not really. But it is considerably more efficient, which translates into reduced fuel costs, and I suspect that it will be easier to maintain, since you aren't balancing carbs, etc. Yes, the new engine will undoubtedly have some teething problems, but this is the direction Rotax is going, so I suspect they will be actively working on solutions - whereas the ULS will eventually not be getting the same attention.
I'm not going to spend anyone else's money for them, but if it were me, I'd probably default to the new engine until I found out more, or that I simply couldn't afford that option.
Paul F. Dye
Editor in Chief - KITPLANES Magazine
RV-8 - N188PD
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)