Go with AGM's. Yeah, more expensive, less performance, can't "play" with
them, etc., etc. However, the electrical loads and starting loads on a boat
like yours are modest. The cost of AGM batteries is a blip in the cost of
boat ownership. If you take a knockdown or go up on a beach and the
batteries get loose, the last thing you'll need at that point is acid in the
bilges mixing with seawater. AGM's can explode but it's far less likely.

I bought mine at Battery World in Portland. I can't remember what I paid
but it was way less than at a marine store.

--
Roger Long