The pry-out hatches work just fine, though you need to add some turning hold-downs to make sure they can't pop out due to sudden pressure changes (Beckson sells them). Even with vented bulkheads, it's possible for this to happen in rough conditions when the hull slaps the water or a wave crashes on the deck. It never happened to me, but my covers were secured and my bulkheads were vented.

I wouldn't used screw in hatches, as all it takes is some sand in the threads to jam them. I've used the locking hatches and I think they're the best overall solution, but they're more expensive and somewhat heavier than the other types.