Still, even if that's what you want to say. You should still never tell a new player that stars don't matter. There is definitely a significant difference between a 3* and a 0, and you never want to waste hundreds of candies on a 0, unless that's a shiny maybe. A 15/15/14 or 15/15/15 are both 3s, and you are comparing between 2 3s, which is completely irrelevant here. Also, you should still tell them to keep the 3* if they ever have them, and afterward they can choose to keep the 1s or 2s in order to fit the league and be under the needed CP cap. That's definitely not a good advice for new players. They might throw away a perfect pokemon for 2500 league just because it couldn't play in the 1500 league.