Both rounds are equally lousy at stopping. So is the .45 ACP, .357 Magnum, .357 SIG, .40 S&W, etc., etc. Handguns are not the ideal defensive weapon, but sometimes they are all you have. If you have any training at all you will know it is not the power/caliber of the round but shot placement that is critical. A .22 will kill you just as dead as a .45 (or 7.62x25) if it hits a vital zone. I, personally, do not envision myself fighting it out with an armour clad cyborg and so the 9mm will do just fine for me. If you see yourself fighting a Decepticon from Cybertron, I suggest you run as anything short of a 120mm APFSDSDU round will do you no good (and even that will fail). For "normal" street encounters the 9mm is probably a better choice then 7.62x25, unless you have some weird immunity to liability suites. YOU are responsible for every bullet that leaves your barrel and over penetration will get you sued at the very least. If you really need to carry a CZ-52, then yes, the 9mm conversion makes a lot of sense. I prefer a CZ-75, or better a XD-9. BTW, the reliability of a 50+ year old military gun, with an unknown use history and documented failures of critical systems (firing pin, decocker, locking rollers) should not be counted on in a defensive combat situation unless absolutely necessary.
