Celebrities. Most of the magazines do an appetizer of socialite/celebrity looks and gossip; in W it's the main course. W is important if you have a need to keep up with today's rendition of ladies who lunch ("it" girls who do coke?). But if you really want to get into celebrity closets (and bathrooms and gardens), you have to read In Style. Voyeuristically satisfying, it also confirms on a monthly basis that money and/or fame do not buy taste.
Snob factor. With its obsession with brand names and its cartoonishly pretentious editor in chief, Vogue wins hands down. Unlike the other editors, Anna Wintour understands the desire women have for a monthly escape into a more glamorous, luxurious world. Unfortunately, she confuses glamour with cliques, making Vogue only slightly more sophisticated than high school. (She's been known to reject job applicants because their clothes are "too matchy" and to kill pieces because the writer's picture wouldn't look good on her contributor page.)
Not coincidentally, the closest magazine in recent years to offer women anything near the real sophistication they crave is Wallpaper, which was intended to appeal more to men. Wallpaper offers a world in which travel and culture are expected and brains and beauty are natural. While Wallpaper is far too caught up in its own particular brand of style to be of long-term interest or importance, it does get the idea that fashion/design magazines are about fantasy, not reality.
On the other hand, sometimes it's nice to nurture aspirations no greater than figuring out which brush goes best with which chemically processed hair.