I am 6.00 and 183 pounds... Do i need a medium or large? I have always use medium in North Face ski jackets
At 6'1" 175 I have always been a large in Arcteryx.
I'd probably steer you to large as well. I'm 5'11 170 and I go Med. Lge will give you room for a light layer underneath if it's really, really cold. Otherwise you'll be fine with a baselayer, and the jacket won't look baggy.