big vs. small
Mix, I''d encourage you to think about the ''size'' issue differently. Ask yourself the difference between living aboard/cruising a 6-8 ton boat (lighter, production-type 36'' sloop, let''s say, perhaps a Catalina or similar), a 8-10 ton boat (either same length as above but intended for offshore cruising, probably rigged as a cutter...or a lighter 40 footer again of the Catalina type), and a 12+ ton cutter/ketch intended by design and construction for offshore cruising.
Speed will be a function of many things, and may be higher in a smaller, lighter, more easily driven hull (but which may be less intended for true offshore cruising) than in a longer but heavier cruising boat. One reason this could be true is some (many, IME) cruising boats don''t often have high SA/D ratios, as offshore sailing with short-handed crews makes ease of sail handling far higher a priority than max speed potential. OTOH boats intended for larger carrying loads won''t be burdened as much by the same loadout you''d be placing in your boat as boats designed/built to a lighter displacement...so e.g. the heavier, cruising capable 35 footer may in fact be faster in a given offshore seaway than it''s light production-type sistership once she''s loaded down with all your ''stuff'', even with the latter''s higher potential SA/D ratio. As you can see, it can get pretty complex when looking at the real-world variables. I think Calder''s Cruising Handbook does a nice job of giving you a sense for these choices.
A ''longer'' boat WILL cost more to run, in every respect. And this is doubly so for cruising/live aboard boats as most of us tend to make these boats more systems intensive (tho'' they don''t have to be; that''s about the crew and not the boat nor its size) and they are of course more heavily used (wear & tear, etc.). E.g. we''re currently cruising a 42'' ketch. We love the space, the ease with which we can take on guests, we like the fact its size makes a watermaker, just as one example, an option (which we don''t choose) vs. a requirement, and motion in a seaway is relatively comfortable. We cruised a 35 footer before that and found it much easier to manage in confined quarters (which usually is the case when out cruising); it was also simplier and cheaper. We''d go back to that size if the other realities of selling one boat and buying (and customizing, which takes $$ and LOTS of effort and time) another were different. The first two boats we cruised were 27'' and 24'', far simplier, far far cheaper, and we probably had the most fun on them...but were the least comfortable and, in both cases, the cruise was intended to be 6-12 mos. vs. the open-ended cruising we''ve done since then.
Last point: try to firm up what you mean by ''cruising'' - it''s a hugely overused term than can mean many different things...and results in lots of mixed advice on BB threads like this one. If you want to reserve the option for it to mean ''crossing an ocean'' type cruising, you''ll have to be much more thoughtful and selective in your shopping than if you mean ''visit the Caribbean'', which damn near anything can do and does (eventually, perhaps ,with some glorious sea stories you can bring back with you).
WHOOSH, currently lying London, England