What you're missing here is that in colder climates, like Rick and I are used to, when you go out in winter if you sweat and you can't get the layer off, you die.

I'm all for breathable and the like. the problem becomes one of when you stop. assume for a minute you know you're not going to get rained and snowed on, so you needn't worry about that.
You still have the issue that doing any kind of exercise in snow you simply sweat. some of us
profusey. Now at milder temps, I don't worry too much, I may sweat the heck out of a base layer and fleece, then stop and shelter myself from the wind, throw a layer on and allow it to dry from my body heat. This works pretty good until you get really really sub zero like down in the low -teens and -20 centigrades. Once I get down that cold I find I can't generate enough body heat to dry that sweaty layer in time without getting real cold real fast, or cover up with a big insulating layer, that at those temps, you're then *frosting up* with the sweat evaporating out of your wet base - wetting out a down parka because you're wearing it over a sweaty base to keep from freezing really sucks.

It's never as absolute as it sounds, you can get a little moist and be fine. but a heavy sweat
and sopping clothing at canadian winter temps is a serious liability. You can carry an extra
change, but then what do you do with the wet stuff? - if you have a hot tent or a fire you can dry it off, alternatively, you just need to be real careful *not* to sweat a lot, which isn't a lot of fun or
very easy sometimes.

Now my personal tactic is a combo of both, I take it a bit easy and/or I do have an extra set of
base layers with me in winter that when stopping I can full change, and build a fire to get the old
set reasonably dry again - in my climate (extremely dry when it's cold) it doesn't take too much.

You're totally right in that it's just like a wet suit - it is. I personally don't like the feel of VBL liners in bags, but I've definatley used VBL socks (they're wonderful, if clammy) and see the attraction
to trying vbl clothing. The alternative is constantly trying to dry out wet stuff and having to
change. A gore tex outer does not help. freezing temps change everything, especially once the
water vapor will freeze to frost *below* the layer of the gortex - won't happen much in milder
temps (even below freezing) but once you're insulated enough to be stationary at -20 you better believe it does.