I'd give the eastern a slight edge, for several reasons. First, I do like the extra day at sea. Second, I like that the Sunday is at sea, rather than in port. After the initial runaround of traveling, boarding, reserving, the sailaway party, and then closing down the clubs, it's nice to relax with a day at sea. It's hard to get up early on the first day and get off the ship. Once in Key West, it was all I could do to get up, eat, and make our 12:30 excursion (Fury Catamaran, which is really fun, by the way). Sure, I could take it easy the first night, but it's really hard to make myself do that. Also, like a lot of people say about Nassau, I can really take or leave Cozumel. It's really my least favorite
DCL port.
Still, I've been on the western twice. It's a nice change of pace from the eastern, and I like the DCL atmosphere, so I'd do the western again without hesitation. But given a choice, I'd vote eastern.