CBR250RR has a different frame than 250R, engine is mounted lower down and it has a lower sitting position ,I think.. from riding experience, didn't really measure it

Not sure about the engine internals, but the 250RR redlines at 19,000 rpm while the 250R redlines at 18,000 rpm..

Most obvious difference is the 250RR has a twin disc brake at the front compared to single disc setup on the 250R..