There is no boat that is just "the best boat', everyone has different need, wants, abilities, capabilities and plans. A friend of mine has a boat that is way different from mine, his needs are different.
Do you plan on staying at the dock
most of the time or sailing off into the tropical sunset. Is it you or a family
....if you sit down and figure out all the specifics of your situation it will be easier to rule
out what will not work. With out a doubt the most important thing in any live aboard is space. Most boats are designed for weekend coastal cruising. I am a sailor so my boat is terrific boat which I plan on sailing the Pacific in....the best boat for a live aboard, that isn't going anywhere is boat that started out it's life as a commercial
boat. I was seriously considering getting an old fishing
boat and converting it, lots of room even before you pull out the fish
holds and the fishing
industry in this country is going down hill fast, not hard to find a good boat cheap
(just make sure to have it surveyed).
For a sailboat that is inexpensive, roomy and sails
well old Catalinas seem to work well, spacious below, lots of head
room as an example.
A friend of mine built a boat 30 years ago and told me one thing "Think of what you will be using it for" he is living very uncomfortably on a boat designed tp do something else.