Chip spec wise yes. But 3GS has the SGX535 gpu heavily underclocked as far as I know. To a quarter of its actual frequency. Where as N900's SGX530 is clocked at full speed. So technically N900's GPU is faster than iPhone 3GS.

Fluidity has nothing to do with HW. Maemo 5 is the issue. If Maemo 5 had QT4.6 and if the gui was based on that also, it would be far smoother. Try the QT4.6 demos to see for yourself. I expect Meego to be very fuild.