Both are correct and widespread :)
There are many equal types for the third plural person of the verb μιλώ such as μιλούν, μιλούνε, μιλάν, μιλάνε, ομιλούν, ομιλούνε. Their use differs from place to place, but all of them are understood by every Greek speaker.
Wow! What a revelation! Does this baffling diversity apply to many other verbs too? Or specifically to the verb μιλ(α)ω, perhaps in other persons too? Is it something to do with the Greek diaspora, or the erstwhile καθαρευουσα?
Verbs ending in -άω have two different accepted forms. So μιλάω can be μιλάω (μιλώ), μιλάς, μιλάει (μιλά), μιλάμε, μιλάτε, μιλάνε (μιλουν, μιλουνε). My Greek teacher said that the forms in parentheses are alternate forms and for formal Greek one should first learn the forms not in parentheses.
Hope that helps.