What you finally decide should depend on what you are planning to do with the kayak. Will it be just for day trips? Weekends? Touring? What type of conditions will you be paddling in? Calm? 4 foot seas or less? 30+ knots? Exposed shore line or smaller lakes?

I use my boat for extended tours in the Pacific Northwest in some pretty nasty stuff so I have bulkheads with hatches and then use float bags to make up any spare space I have after I pack in the dry bags (loaded with gear). I also make sure when I load the kayak it is equally distributed. My thought is if the hatch leaks or blows off, I have the storage space filled enough so as to not let much water in. Overly cautious? Maybe, but I've at least got another line of defense against one problem.