I would pick October because we love to swim/do the water parks. Although we live up north now, we are southern born and bred....therefore, we do NOT swim when it is chilly outside. Even though the pools or heated we hate getting out of the water when the air is cold, as Janurary usually is (to us anyway.) October is almost always still warm, but not broiling. We went last October around Columbus Day. This year we are going for Christmas and the kids are already complaining that it will be too cold to swim (most likely.) The hurricanes are usually over by October, but that could be a problem some years. Janurary would most likely be less crowded, so it just depends on what you want to do. Walking around WDW in a coat and gloves is just weird to us, but I guess if it was just dh and me it would be okay!