I try to buy, and therefore to own, whatever sort of boat gets me the most boat for the money., in terms of first price and ongoing costs. When I was young that meant wooden boats of a non-racy type. Now I am old that means plastic boats of rather racy type. Having started off with jolly small boats, which were all I could afford, I’ve never been much concerned about accommodation, as long as the decks don’t leak.
I've owned my current boat, a Jeanneau Sun 2000, for longer than any other boat. I started small, worked my way up to 44ft and all the way back down again.
I find the thing you really need in a small boat is performance to actually get anywhere. The Sun 2000 is not the best performing small boat (I imagine something like an Elan 210/21 would be near the top), but it is certainly near the performance end. I managed to get 9.5 knots out of her once, single-handed with the asymmetric spinnaker in a force 6. I did broach in the end, but was rewarded by a good action photo by David Harding!
Next is accommodation. You're never going to live inside a small boat, so the only real requirement is decent length/sized berths. Everything else (cooking, bucket loo) can be done outside in the cockpit, under a tarpaulin, if necessary. The Sun 2000 scores in having a cockpit that is as big as most 30-35 footers.
Finally would be shallow draft or the ability to lift a keel. That way you don't need a tender (I step off onto the beach, use waders or swim) that you have nowhere to store easily and you can always find a berth in any harbour at any time.
Going through that list, just reminds me why I haven't been tempted to change boat!