I think that the higher training you get then the better tamagotchi character your tama will evolve into. If you give your tamagotchi a praise when it needs a time out or if you give it a time out when it needs a praise, then it will almost be certain that you will get an average or a bad character. I hope that I helped!
The higher score you manage to get on your training bars, the "better" the character is - usually healthier (strong, not weak) - so more likely to win games and also when an Adult, loses happy / hungry hearts more slowly - so it doesn't need so much constant checking.
(Often gets nicer presents when connecting with another tama too!)