You know, not that I would turn DOWN a house, but like in Oblivion and Skyrim, I actually prefer the smaller, more nondescript houses that are more likely overlooked... I don't know but it helps me RP more. In Oblivion, for example, the little cozy run-down house in Leyawiin was my favorite...
Anyway, in XIV, I think medium would be the largest I would want for my personal house. Large is so big... feels kind of empty all by yourself... maybe...