Which 4 season camper would you recommend?

One thing is certain --- if you are looking for a cold weather unit, it won't be a "lite" trailer. Things like enclosed underbellies, insulated valves and other insulative materials cost money and add weight. There is no magic. It sounds as if the OP is exercising due diligence, and I congratulate him for that. For others, keep in mind that "four seasons" means something very different in the north than it does in the south or (most of) the southwest.