Too many variables involved to simply say class A rigs across the board are better for cold camping than 5ers, TTs, or class B/C rigs. One thing for sure is any RV can be easily modified for cold weather use, we have done this to every RV we have owned over the last 3 decades including our current class A Monaco. We do lots of sub-freezing camping but not for weeks on end, usually a few days is plenty as we do like enjoying the outdoors without freezing our tails off. Truth be known, RVs are just not designed to withstand long term below zero extreme cold usage from the factory.
As we got older and now camping without our kids we went from having 5ers, TTs, and toyhaulers to a class A rig, it is easier overall which keeps my DW happy, she was losing interest in RVing and now is invigorated to set out for our next excursion. We took our time researching the many aspects of motorized RVs, drove as many as we could to help decide which chassis and drivetrain we felt suited us best. Doing your homework is critical for motorized RVs, getting it wrong could cost 10s of thousands of dollars of repairs down the road and severe loss of value when reselling.