While I'm sure any of those could work for living aboard, some of them do look a lot homier than others. I think if you can look at interior photos of a boat and not immediately conclude that it's a boat (or a bus or a trailer, etc.), that's probably a good thing. Even if you're well prepared to live in a relatively enclosed space, you want that space to be comfortable, right?
With that in mind, the 55ft long Commander is my favorite. But at the same time, you said you wanted something shorter than 45 ft. if at all possible for the sake of maneuverability. With that constraint the Vikings look good, though the Silverton might be a better deal.
Hi.
I think its a good sign of a quality builder if they incorporate livability into the space. Some manufacturers are just better at design than others. And some boats have "weekender" purposes and aren't meant for living long-term. Kinda like a hunting cabin, it'll suffice a bunch of men who want to fish, drink beer, and dump their poop when they come back. Those are the ones shaped like Corvettes, instead of having a big fat ass on 'em. I like the shape of the hot-rods, but they would suck for living. You need big holding tanks for water and waste, not just fuel and ice chests.
So it kinda bums me out when the ones for living aren't sexy from the outside. Thats one of the reasons I like the Silvertons, too. They have a nice shape. Its a mental obstacle I have to personally overcome, because 99% of the time, your view will be from inside. You won't be standing on a dock watching your own boat run past, looking like tits-n-ass covered in whipped cream.
The size is ultimately important in a number of ways. Boats weigh a ton. Pushing that weight through the water is a huge energy burn. Drag is simply massive in water. They are so totally inefficient, its really just disgusting to consider in terms of fuel consumption. A twin-screw (2 props) diesel with normal sized engines can rip through absurd quantities of fuel, regardless of boat size. It can cost you a couple hundred bucks just to move it a hundred miles.
Heres a photo of a typical diesel engine room. Note the headroom is about 6ft high, so a person can work on the engine.
Thems some big fuckin engines. I don't have the specs, but thats what you'd probably find in most of the boats I pictured. Give or take, those are Detroit naturally aspirated 671's. Common engine, sometimes they're under the floorboards and you pull the sections of plank up to access. Thats why you see square sections in the carpeted floor of live- aboards. They don't always have an engine room.
Suffice it to say, larger boat compounds mightily in fuel consumption.
The thing is, you want to run your boat. You want to run it and enjoy it, this is the purpose of life, and life on water. Its kinda fucking pointless to own a boat and not run it. So you'd want to minimize the financial impact, and maximize your ability to steer it with any degree of skill. You would not want a monstrosity that is beyond your abilities of skill.
Boats don't have any brakes (although you can reverse the engines). Momentum is a bitch. You can crash into stuff and with 60,000 lbs of kinetic energy behind a mistake, you can do a lot of fucking damage. You can crush your bow, collapse a dock, or crush another boat. The longer and bigger, the less forgiving it is. Energy in motion is a mathematical fact, and mistakes with weight behind them just keep on crushing in slow-mo until you wanna puke.
The weight that would make sea-going more comfortable makes maneuverability more hazardous. In the water, the bigger the better when waves are a consideration. At sea, you want a big fucker. At dock, you want a small boat.
I would love to have that brown Constellation. And I'd probably bite off more than I can chew, and opt for it like a stupid man. And I'd probably kick myself for years after, because its just not practical. It'd cost me a couple hundred extra per month in dockage, and a couple hundred every time I wanna run it. And for what? An extra bedroom I never use. Boat length is a dick measuring contest, and the rules of land-lubbers with house size need to be checked at the door. They do not compute. Photographs screw with your eye, and make all boats look small inside. Boats are 15ft wide, which is bigger than the average bedroom. Its a quirky thing when people photograph the inside, they take photos down hallways and from doorway vantage-points. The windows are small, and the doors are narrow for reasons of structural integrity. Conservation of space in kitchens and bedrooms is an art form which translates badly in photography. They also employ low ceilings for structural reasons, which is unnatural to the eye in people who are accustomed to traditional architecture.
You'd need to go aboard and physically adjust to the surroundings. A 40+ may be more than adequate.