Hmm, I've been skiing and boarding for close for 40 years now (does that make me ancient school?) and have worn almost every conceivable fit and style ranging from the hippie jeans/plaid jacket in the early 70s (wet, cold and uncomfortable), to a technical Bogner one-piece in the 80s (never again--impossible to go to the bathroom, but it helped me win a couple of races!), to baggy skater style in the 90's (pockets, fleece, and duct tape galore while I learned to board), to high-tech skinny in the 00s (can't pronounce the fabric or insulation--too many syllables), to the rather sedate fitted pants and down jacket outfit I'm currently sporting.
My thoughts: If you buy REAL slim-fit ski pants (not indoor lookalikes), they can keep you just as warm and dry as baggy pants, so it's really your choice. Style varies from location to location and within the cliques on the hill (bunny-hill style is different than black diamond style). Locals ALWAYS look different than tourists because locals spend so much on equipment that not much is left over for clothes. Boarding gear differs from ski wear, so it usually is best to decide what will be on your feet before choosing your outfit. And warm weather skiing in cement (ugh!) requires different gear than heliskiing in the powder (absolute bliss!) so that might also influence your outfit.
