I would say that your questions are subject to personal preference and subjectivity rather than dispute. I could take umbridge with Camaradie's comment "I think a lot of the "under 40 ft. crowd" recommends this because the writers asking for advice are inexperienced sailors AND because the responders themselves own under 40' boats and have a bias towards that size range." , but I won't. As someone who has sailed on boats of a wide range of sizes, I really think that the choice to go under 40 feet is one of preference rather than saying the decision is budget, or lack of experience driven. Just in the same way some people prefer to drive sports cars, or high quality compact cars, rather than an SUV, some people simply prefer living aboard and sailing smaller boats as well. I live very comfortably in an 1,100 square foot house, but I am designing a 9,500 square foot house for a client whose life style requires this much space. Neither of us are any more wrong in our choices or any more right in our choices. I doubt if I could afford it, that I would buy a bigger house or a bigger boat, but that does not make me univerally right, if you see my point.
For Camaradie less than 50 feet is not a comfortable size to live-aboard. For him that may be true. When I was in my 20's I lived on a 25 footer. I found her quite comfortable and at one point found myself asking, why would anyone want something bigger. As a kid, in the 1960's my family of four lived on a 32 foot Vanguard rather comfortably. My rather small 38 footer seems quite sumptuous to me and a good size between ease of handling, performance and seaworthiness. I look at my father's 42 foot offshore cruiser as being too big to be convenient, yet he has lived aboard quite comfortably, found her quite to his likeing offshore, and handles the boat quite easily with my stepmother.
What I am getting at is when you talk about the right sized boat, it is all about your own personal needs and tastes. Camaradie not wrong, he's just not universally right either. None of us can answer for your needs.
Lunch hour is over so I won't get into my disagreement in point of view on the quote "but many like me find [Tartan's, Sabre's etc.] unsuitable due to hull design and/or resulting lack of comfort at sea."