I've never actually backpacked in a place where I thought something like chaps would be necessary.
If you're brushbusting where there's snow stuck up on brush (wet snow) they might be useful in keeping your pants dry. But I kind of see that as a pretty uncommon situation. Usually places where you need to bust brush like that a long ways in deep and/or wet snow, I'd rather not go there or just go around the brush. Or stay home/dayhike instead. I really, really dislike being both cold and wet.
Most of my backpacking experience with snow is way up in the mountains, and usually up there the snow is hard enough you only sink in a few inches, or not at all depending on the time of day and temperatures. When I'm where there's brush, we are usually pretty lazy and go around stuff thick enough that it would tear up our pants.
To be honest, tin cloth is pretty heavy stuff, and something I'd rarely consider for backpacking. It may be different in environments other than ones I'm familiar with (high alpine mountains and open Nebraska prairie), but the tin cloth chaps wouldn't be high on my packing list.
