Well, there is good and bad Tamagotchis, and there isn't good bad Tamagotchis...
Well, all Tamagotchis are good in their own way, but there are healthier and unhealthier characters, unhealthier characters lose hearts and poop more often than healthier characters. It depends how you treat your Tamagotchi whether you'll get, an unhealthy or an healthy Tamagotchi. I mean care, discipline, snacks/games...
yes, all of them are great in there own way and you should be happy with them. But some tamagotchi you get by a certain way you treat it. treat it bad, you get a certain character, treat it good you get a certain character.