Aspen: 4 mountains (Aspen Mountain, Aspen Highlands, Buttermilk, Snowmass), 5,500+ acres, more nightlife, smaller town walkable, celebrity scene, more challenging terrain (Highland Bowl). Vail: largest single ski mountain in US (5,289 acres), 7 legendary Back Bowls, family-friendly Vail Village Bavarian style, Beaver Creek nearby for more luxury, easier access (closer to Denver). Cost: similar ($200+ daily lift ticket without pass). Both have Forbes 5-star hotels. Aspen better for: nightlife, advanced skiers, celeb spotting, varied terrain. Vail better for: families, intermediate skiers, more lodging options, longer ski season. Both: Epic Pass works at Vail (and other Vail Resorts), Ikon Pass works at Aspen Snowmass.