I think I'm one of the few people that have had both. I had a 2012 AF 1150, then got a 2012 EC 1160, both pretty big ones in their respective lines.
Cold weather boon docking, I do a lot of that. Did it up in the mountains for Jeeping in the winter, and also go out to the WA coast in the winter.
My comparisons are all my observations, not just cold weather boon-docking. But in regards to cold-weather alone, I can't honestly say I have major pluses or minuses for either.
* Both are well insulated. Arctic fox does have it beat by a very small margin - I went through maybe 20% less propane heating it.
* Both have heated basements - The way Eagle Cap does it keeps the basement much warmer. AF uses a small box fan to circulate air, EC uses the entire furnace intake through the floor and into the basement. But pushing more air through the basement makes me think this is why I go through more propane in the EC.
* Tanks - EC wins for water. 75 Fresh, 32 Gray, 28 Black.
AF wins for black tank - Fresh 59, Gray 35, Black 43
* Storage - EC hands down. At least for my model to model comparison. I can literally crawl up in the huge rear storage of the EC.
* Floor space - again, EC hands down. The AF's floor is in between the bed rails, so only 6foot-ish is all the wider it can be. The EC is up over the rails, a full 98" wide. Night and day floor space.
* Because the floor in the EC is much higher, the step from floor to the bunk is only about 24". AF was 3 feet-ish.
* My EC has a sofa AND a dinette. This and the floor space is the reason I sold a near-new AF to get a near-new EC.
* My EC has a Heki Roof Vent in the bunk - it's huge and has an integrated cover, I love it.
* Much bigger bathroom in the EC - VERY small "toilet space" in the AF, and also a comparatively small shower.
* Weight - my EC is much heavier, but this is not inherent to the EC line, I have their second biggest double slide TC, so just an issue with my particular model. You need a DRW, F350, F450 or F550. I've **seen** people hauling around the bigger AF's on a SRW, but I don't recommend it.
I'm sure I'll think of more stuff, I'll edit this if I do.