A couple of things to consider: Your charger, what type of batteries can it charge? Reserve amps or reserve capacity (the number one thing to consider in deep cycle batteries).
You mentioned sealed. There are two types of deep cycles that are sealed: flooded cell and AGM. If you go with AGM then be sure your charger wil work with them.
On flooded cells be sure to get at least 180 reserve minutes or you may run out of juice before the day is over.