I know this is an old thread but thought someone might look at it again.
I fly a Kitfox 7 SS with a continental O-200 (on 26" ABW). I have also flown a 7SS with rotax912UL (on 8.5's) and a 7 STI with 915is (on 31" ABW). As much as I like my plane, the performance difference was very notificable. Both rotax out performend my plane in climb and cruise.

I get about 95 mph in cruise at 2550 RPM. The 7SS 912UL was at 120 mph. The 7STI 915is was 115 mph.

at sea level the 912UL had about a 200 fpm climb advantage over mine (flown the same day)
at 5000-6000 ft altitude summer day in Idaho, the 7STI 915is had about 800 fpm climb advantage over mine. Also the STI wing dropped the landing speed by about 10 mph (I have not put VGs on mine yet and he had VGs also so that will play a role)

Takeoff roll was barely noticable between mine and the 7SS 912UL (maybe 50 ft), but the 7STI 915is cut about 100-150 ft off the takeoff roll even in the mountains in the summer.

I have no experience with the titan engines.

Hope that helps.