I prefer a griddle pan as it's easier to clean!
My brother and sister have both got a George Foreman grill, but I always found it hard to clean as the grill plates didn't come off (although I think on some models they do)
the trick with those types of grills is to wipe them down while they are still fairly hot, before the grease has time to set.. it's so much harder to shift it once it's cold..