I`ll throw in my 2 cents and say what everyone else is pretty much said already. Size is a matter of comfort not seaworthiness. I don`t think anyone wouls question the seaworthiness of a Bristol Channel Cutter. So it basically comes down to preference and comfort level of the crew. I personally prefer boats less than 30 feet. I lived and sailed on a Cal-29 for 2yrs and never wished I had a larger boat. Thats not to say that one day I will not have a larger boat.
Each has its own set of advantages and disadvantages.
Then there are those microcuisers
http://www.microcruising.com/