The instance Bato instead of Vato should be more appropiate as it sounds on the streets. But grammatically, both words are correct because this word hasn't been ruled by any Language academy so far.
Vato is not the same as güey. Güey does not implies respect. Güey is more alike to be pejorative or familiar depending the way it is applied.
Que pasó vato, hace un buen que no te wachabamos por acá en el cantón...
Saludos desde Juaritos Raza!!