Obviously, everyone has their favorite hill
Where will you be staying? Downtown? N? S? E? Are you out for a week of fun, or are you squeezing skiing on on the weekend during a business trip? What kind of transportation will you have? This info would help frame the discussion a bit. Lots of good choices. The "best" choice, however, will depend to some extent on timing & logistics.
Also, the areas here pretty much rely on mother nature for snow. So, depending on the year, things can be great all over, crappy all over, or very variable. Variable can mean one area has tons of snow and another nearby area is full of rocks, dirt & plants. If your itinerary allows, you might want to finalize your plans at a much later date - once the snowfall situation is known.
For some reasonably accurate/reliable info, check outSki & Snowboard America Pacific Northwest and British Columbia
As has been mentioned, virtually all the areas are better during the week. Weekend crowds can make the areas closer to Seattle miserable relative to mid week when lines are usually a minute or two long. Also worth noting, both Stevens and Snoqualmie have significant night skiing operations.[ October 25, 2003, 10:43 PM: Message edited by: spindrift ]