For the last few weeks I have had a survey running on my Summit County real estate blog, asking people which is their favorite Summit County Ski Resort. Copper Mountain took the lead early on (I only voted once!) and is now way ahead of all the other resorts. 
Today my SKI magazine came in the mail and I found Breckenridge listed at #7 in the west, which put it as #1 in Summit County. Breck has never been my favorite mountain, although I know many Summit Countians that won't ski anywhere else. I have often found it cold and windy, (AKA Breckenfridge), crowded, and hard to get from one area to another. However, I have had some great lessons there with the Professional Ski Instructors of America (PSIA) and last year I was introduced to the T Bar. I guess if I skied there more I might like it better.
The night life is a big draw in Breck. There are many wonderful restaurants and plenty of things to do apres ski. It has arts and culture with galleries, neighborhood playhouses and summer concerts. The town and the ski mountain are interconnected with the gondola and a great bus system, and many condos are within walking distance of both. 
Keystone was rated number 11 by SKI magazine readers and it has tied for last of four (with Arapahoe Basin) on my very unofficial and unscientific survey. Keystone has the advantage of being part of the Vail Resorts family, together with Breckenridge. The season passes work in both areas and many out of town visitors will ski both mountains during their stays. Keystone has some fun tree skiing on the Outback and North Peak has nice runs when the snow is good. I avoid Keystone during low snow conditions and in early season as it can be icy. I have yet to try the snowcat skiing, but I have heard wonderful things about it!
Number 14 in the west is Copper Mountain. My readers gave it a number one rating with about 2/3 of the first place votes. SKI magazine calls it underrated and says that some people like it because it hasn't been "Aspen-ed" yet. I would agree; it is laid back and relaxed, with no need for pretention. It does lack evening activities, but Frisco is nearby with some great restaurants. Copper brings in a lot of weekend events that keeps things exciting. Pass holders are very loyal and now are excited that is possible to ski at Winter Park and Steamboat with as some of the pass products. Copper skiers have options from easy beginner skiing to extreme "hike-to" skiing on Tucker Mountain. At Copper, skiing is what it is all about.
Arapahoe Basin, "The Legend" also has some extremely loyal skiers. There are many telemarkers and back country skiers that frequent the areas in and around A Basin. Of course, it gets many late season skiers after other ski areas close. It is a mountain for die hards; bumpers, extreme skiers and adventurers. Pallavicini, affectionately known as "Pali" is a goal for many intermediate skiers proving their skills just in getting down it.
All four Summit County ski mountains have lots of things going for them. We always hope for upgrades and improvements, and we usually get a few each year. Often, one mountain will get lots of new things that pushes it ahead of the rest, but then the next one will catch up and become competitive again. Skiing and snow conditions are of prime importance to the local skier, while accomodations, food and nightlife might be more important to the destination skier. Together, they show that competition is good, and they do a wonderful job of serving a variety of needs for the skiing and riding population.
Joanne, I just stopped by your site to vote. It would be interesting to see what the results were if you asked what the favorite area is for the summer.