I don't think we're talking about a strictly home defense gun here. More concealed carry.
That said, why in the hell WOULD anyone want to rely on snake shot to stop a human? Has anyone thought that maybe, just maybe, some crazed or drunk or stoned criminal might become ENRAGED at being shot by something that will do little more than agitate him?
All reputable sources on the issue advise using pistol rounds that get at least 12 INCHES of penetration and expands reliably. Any modern, brand name hollowpoint will fit the bill here. Most reputable sources on the subject dismiss snake shot as next to useless.
As for overpenetration, by the time a hollowpoint has expanded and is done popping out the backside of your attacker, I doubt it will have much force to do any serious harm to someone beyond. If you are cheap, though, and don't get a hollowpoint that still expands despite clothing, you could be screwed.