fuel injected bikes are easier to start, and run better in cold weather or changing altitudes... as far as being more user friendly, the throttle response is better on carburated bikes, more immediate and smoother when you get on the gas, the fact that newer bikes are run alot leaner and i guess just the nature of a electronic fuel system means there is a slight delay when you open the gas or sometimes its a little jerky

as far as race gas its not worth running in either, sometimes at track days if i would run out of fuel or forget to bring some i'd buy race gas and it never caused me any problems but its not going to give you any benefit