If I could only have one of the two, hands down a 9mm. If I could only have one gun (awful, right?) at all, it would be a 9mm handgun. Carry, HD, plinking, survival... A .22 just doesn't cut it for power and reliability to use it for any form of defense, to me. And a 9mm will kill a squirrel just as dead as a .22 if it came to that. A 9mm will stop an attacker much better than a .22 if it came to that. Fun for the dime, I think 9mm is still 3rd behind .22 and 5.45x39, but it''s no contest as to which I would take if I could only have just one.