I'd go with Aqua Traction over Seadek. AT is closed cell, more dense and easier to clean. I've also had Seadek and feel AT is a better product. Just my 2 cents..... Here's a pic of my 08 2320.
I did my 2003 2520 with Dekit which is a much more superior product than seadek. Just like firerider4 mentioned about aqua traction it a much more dense closed cell foam that cleans up easier.