Well I know that the 2650 on 6s will spin over 50-52K rpm and the 2200 will spin in the 40-44K range so for longevity the 2200 will be your best bet. The 2650 may be faster, however, it won't last as long spinning that fast
Ok now think about this what if I advance the timing to high wont this be techniclly adding kv's to the motor?