I looked at both the R1R and AD08 2 years ago when i needed something to go on track with, as i recall it the AD08 is a bit harder compound that the R1R. Also i've heard from some guys in Denmark runnig the yokohama cup that the AD08 is noisy and lacking grip when really giving it the beans.
At my level of performance the R1R is the perfect tyre in between the R888 and Michelin Pilot Super Sport, so it's actually the best of both worlds. The grip is awesome and it's an easy tyre to read. I've done app. 13.000km on them including trackdays and there still rubber left to make them roadlegal
All in all you won't be let down by the Toyo R1R's