Many boats do have a 'convertibe dinette' that can make up a good sized double with plenty of headroom, but I can tell you that making that berth up every night and setting up the table again each morning gets really tiresome.
Way up on our 'must have' list on our last boat purchase was two 'doubles' without the dinette.
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"