As a rule I always go with trainers with ‘good training ability’ and ‘excellent in developing potential and talent’. I will sacrifice other stats to yellow as long as these 2 are in green. My thinking being that these stats contribute to improving your boxers stats more.
But do they? This is a hard one to judge just by playing the game. Is there a difference in development if you have these stats in yellow? Does it affect attribute points at all?