I wouldnt recommend a .32 cal revolver. Ammo is hard to find. If you do find any it's .32 S&W Long, short @ $30 a box for round nose lead. Watered down cowboy action rounds
1) .32 Long is quite popular outside the USA and can be readily mail-ordered online for ~$15-$17/50rds in quantity. Like other relatively unpopular small-caliber cartridges such as .25ACP, it's expensive only because local gun stores overcharge for it since it's a slow seller.
2) Commercial .22WMR rounds are loaded with bullets that are ill-suited for SD against humans; they either won't expand at pistol velocities or will violently disintegrate without penetrating adequately. You're better off going the non-expanding route, and that said, a larger hole usually beats a smaller hole.
3) It's designed to work from a short barrel and lacks the .22WMR's tendency towards ear-splitting noise and blinding muzzle flash from a pistol-length barrel.
4) It's centerfire and therefore more reliable. It's also less dependent on a heavy mainspring- and therefore a heavy DA trigger pull- for consistent ignition in a revolver.
5) It lacks the .22WMR's reputation for fouling revolver cylinders.
That said, .32 Long still comes up short versus cartridges in the .380ACP or .38Spl class, but I'd take a .32 Long revolver over a .22WMR revolver any day of the week.