Well here we go
Well first anime:
1. Hazuki: Yeap, he haves the skills to become one and including the team, very balanced
2. Satoshi: Determination, that's what makes him stronger and he never give up when he battles
3. Haruka: Maybe she doesn't battle in Gyms but she haves skills to be a great trainer.
4. Kenta: Sure he haves a strong team, and a strong will too, that's what makes him a strong battler
5. Yuuki: He must be good, so he's an excellent candidate
Now the manga:
1. Red: He haves a strong team and a strong will to battle
2. Green: He haves a very balanced team, including great strategies
3. Gold: He left to train to the Silver Cave, so for sure he got a lot stronger
4. Sapphire: She is really a good battler! But she needs to make her team a bit more balanced
5. Yellow: She haves a good team, but what she needs is training, still she can be a Pok?mon Master
That's all what do i say ^^