i had an XR3 then chopped it for XR3i in 1985 the better car was the non -injection done the same with a UR quattro then got S2 the UR was far more fun!!! had a Z1B then had a ride on a Z900 the difference was worlds apart- the Z900 was far better- not such a beast but handled better
Compared to my Kwak 500 H1F my GSXR1100K handled a hell of a lot better, but was futher improved by the addition of a Harris Magnum 4 body kit. As for Mopeds FS1E was ace, the AP50 a better bike but both were far to refined compared to a Fantic Caballero.
No direct experience of a 999 although I have a project in mind that includes a Single sided arm. Currently settle for the blend of old and new 748RS Chassis with the later 998 Testastretta engine. I think its going to be hard to find a bike that is better than a sorted 998R