You know what, I've changed my supporting mind. Let it not be said I'm not someone who cannot be convinced...
Anyway, I'm voting Fighting now.
Besides the fact I can foresee a Electric/Fighting type being possible and removing lots of problems for us, Fighting presents us with resists to SR, Pursuit and U-turn, which are all very useful for counters, and it isn't restricted to a certain moveset either, provided we don't decide it's another muscle-bound Pokemon which can only use certain moves. Which isn't the eptimone of a Fighting type - as Breloom shows.
Regardless, it doesn't honestly matter - both types are equally good, with their weaknesses counter-balancing their strengths, and everyone agrees that both types are fairly easy to customize. We aren't restricted to a certain design, save the Utility Counter. So it's a win-win regardless of the winning type.