The Pex and plastic fittings are more sanitary, don't required thread goop or tape, are typically hand tight, don't corrode, don't have issues with electrolysis, and I think they survive better in a freeze. My daughters truck camper froze and the only thing that broke in whole camper were two copper lines.
On the fridge, I was referring to the ice maker. There are a few threads here where folks are having a hard time figuring out how to drain them without pulling them out of the hole. May not be an issue because you will have the outside vents from your old fridge to access the ice line, but the factory residentials do not.
I realize your furnace quit, and I feel bad for you - just wanted to comment that you are probably better with the plastic than the copper.
Brad & Dory - Lone Tree, CO
CURRENT - 2013 Itasca Meridian 42E/2013 Wrangler 4dr Sahara
SOLD - 2014 Redwood 36RL/2014 F350 DRW