A portion of a GamePro interview with dev Takeshi Kawachimaru and composer Junichi Masuda...

GP: Do you have a preferred type [of Pokemon] that you use when playing the game. What is your preferred lineup? What are your heavy hitters?

Kawachimaru: We have an internal office tournament, so whenever we battle, I predict what my opponent will have, and then decide what my Pokemon will be. But my favorite Pokemon to use in the tournament... there are two of them I regularly use. One is Weevile and the other one is Gengar.

Masuda: The type I always use is actually Water Pokemon, because Water Pokemon have strong moves, such as Surf. That's my favorite move. Also, I get involved in creating Pokemon itself, so I get involved in naming, get involved in the design of the Pokemon, so there's so many Pokemon that I have so much energy put into, so those are the Pokemon that I always want to use. But, that's not necessarily a strong Pokemon for the battle.

Full interview here