My thoughts, for what they're worth...
That 50' Beneteau is an awful lot of boat, for someone's first... Way too much, IMHO... Especially for a sailing ground like Lake Superior...
Placing such a high priority on headroom is misguided, in my view... And certainly not a good reason for going for something larger than you really want, or need... Furthermore, there is rarely any direct correlation between headroom, and the length of the berths aboard, 6' 6" seems to be pretty standard even on many boats of relatively modest size...
Headroom and long beds isn't the only thing I am looking for though. It needs to be fairly roomy, easy to sail, with nothing major needed to be done to it to make it seaworthy, and if it all possible not need any majorly expensive things in the future.
In that event, you might want to steer clear of a boat with 8,000+ hours on the engine... ;-)
The one thing that I really like that comes with a longer boat is that I can go faster than the shorter boats because of the hull length, and I love to go fast.
Sounding more and more like you might be better off with a powerboat... In the larger scheme of things, I've never considered the difference between "Slow", and "Fast", to roughly equate the difference between 6, or 7 knots... ;-)
Nevertheless comfort is a big deal for me and I will continue my search at the local marinas and see what it is really like down below. Around here it's rare to see a sailboat over 40ft but at least it will give me a better idea of what it's really like in cramped quarters.
Perhaps something like a week's charter aboard a mid-sized boat in the BVIs would be a more productive means of sorting that stuff out?
What if I want to take it to Philadelphia to visit the in-laws or to NYC to visit my sister?
Do you have any idea what such a trip involves? I recently ran this boat out to Ohio... Trust me, by the time you've unstepped the rig, and locked through for the 35th time, one of those stinkpots with headroom to spare might be sounding pretty good...
I don't think I could live on a boat with only 6'4" headroom for that long.
Seriously, if that is indeed the case, then perhaps living aboard might not be for you...
Oh, and for the record, I'm 6' 5", myself...