Do you find any difference between them?
Good question. I had a lot of gear/accessory component changes happening when the different 242's arrived. Then I experimented with some other exotic power tubes, but never sat down and did any hard core, focused comparisons, regular KR to RK.
I *think* I have a slight preference for RK, but this can of course be system dependent. I'd need to do further testing.
Both versions are really good. Definitely my favorites of current production power tubes. Of course when I say "current production", the RK's were limited production from 6-8 years ago and can't be purchased anymore.