It depends, really. If it's a file I'm very attached to then I would probably buy the opposite version, because then I can keep both of my files, and get game-specific Pokémon too. But if it's not, then I trade my team and start over.
~ World famous singing sensation, Stefan Gordy.
(For the longest time I was telling myself that I would come back to PE2K once I had something artsy and cool to contribute... but that's too much effort. GIRA IS BACK!)