For me then my list of must's is:
Must be able to take my toys, few sets of dive gear including compressor, mountain bike and surf boards. I'm not one of those anally neat storage people, and hate climbing under too much stuff to get what I want so will require a bit more space that many.
LOL- If you truly want to cruise, and if you truly want to cross oceans, you won't last a week until you get tired of your stuff flying around, and you will learn to square away your gear. In other words, you WILL become an anally neat storage person.
Also, remember Murphy's Law of Stuff- no matter how much or how little stuff you have, or how big or small the space for it, your stuff will occupy every possible cubic inch.