first, I've printed 12x18s that side by side next to 1DII, 40D and 5D shots look awesome. You can pixel peep and see the difference, but the subject of the picture is enough to make you enjoy that instead.
Second, if you're taking a 1D skiing/snowboarding GOOD LUCK! It eats batteries like it's it's job. I needed 4 batteries (which are huge, heavy and expensive) to take a 1D on a normal shoot. Cold weather will dramatically effect that, so don't count on more than ~250 shots per pack in the cold.
Third, the 40D is fine in the snow. I take my 5D out skiing ALL THE TIME and it's less sealed than a 40D. If it was raining, then yeah, maybe you'd need a 1 series, but you likely wouldn't be shooting in the rain on snow. Also, the 40D has 6.5fps so unless you NEED the 8fps, it's got more than enough to handle what you're doing.
FYI I sold my 1D for a 40D because of the battery issue. Especially in/around snow.
this is me out with my 5D last winter:
