That keyboardist matter has been discussed for years without a clear winner. IMO, we should see it separating our opinions in some keyboard fields, for example:
-Soloing: KM
-Atmosphere: KM
-Cool new sounds (also bad new ones): JR
-Technique: JR
Anyway, my opinion is that JR could become better than KM if he stopped his wankery (even when playing piano), specially when soloing. However, he has done some great solos, and also brought that kind of special or different moments that didn't exist with KM: honkytonks, some strange progressions, cool new different sounds and moments... However, KM had always that sound that fitted perfectly in DT. It was not necessarily complex, but was perfect. Also, his soloing was more melodic and less wankery.
In summary, JR has a lot more potential, but KM used his abilities better.