Pros: They're white! The cable's not ten miles long.
Cons: They might get dirty. Hard to find for as cheap as the black ones, but cool always costs more!
Just having some fun here folks. The ATH-M50 has been reviewed to death.
Get the white ones! The cable's short and coiled and looks like it came off a white Princess telephone from 1975! They look so much cooler! The white ones are all new production, so supposedly they are more neutral than older production M50's. That could be a benefit or not depending on how much you believe the old "M50's have a lot of bass and recessed mids" legend.
Don't be like those other kids. Get the white ones!