Perhaps the two points need to be separated. You are completely correct in that a win is a win and a loss is a loss regardless of the circumstances.
How about this instead:
It should be noted, however, that playing with lesser Pokemon is not necessarily mutually exclusive to playing to win. A player who prefers to play with "favorites" can still greatly increase their enjoyment of the game through knowledge of competitive battling. Indeed, if attempting to play seriously with an otherwise underpowered team, the skills from high-level competition are even more relevant to level the playing field.
I'm sure everyone has a pet lineup of their personal favourites that they bring out from time to time. This doesn't mean that they're not playing to win, nor does it mean that anyone who beat them was being "cheap".