I think the 22's are better killers than .177's. Even though the 22's have a lower velocity, they are roughly double the weight of the .177's.
I agree with this. I have owned several 34's, decent guns but not in the same league as the R9. Whichever you choose the .22 is a better 'killer' in my experience of several hundred rock chucks over the past 10 years shooting both .177 & .22.