>>54974451Says it right there; Karen makes an argument for skill and the gentleman makes a case for strength. Both are correct.
Winning with your favourites takes far more skill than it takes to use objectively stronger Pokémon instead; and said objectively stronger Pokémon are demonstrably "stronger" on average.
Whether you value skill or strength more is completely up to you to decide; no one makes the case that you need one or the other to be a Pokémon Master but it could be interpreted that way.