One dedicated 20 amp branch circuit to each bathroom is the better install, in my opinion. But it's only an opinion and a design issue. The Code allows for the (1) 20 amp circuit to be "jumped-out" to all the other bathroom as long as nothing else is on the circuit besides bathroom recpeptacles. The Code also allows for lighting to be included on this 20 amp circuit as long this circuit doesn't feed other bathrooms.
