I'm far too biased to give an objective opinion.
My group is halfway through Age of Worms at present (we started it long before WotBS began). I can't wait to run WotBS after it, though.
The differences that aren't "subjective", so I feel it's OK to compare them despite being involved with WotBS:
1) WotBS adventures are much bigger. Paizo's APs averaged just under 30 pages per adventure, including ads and cartoons. So far, we have a 60 page, a 70 page and a 100 page adventure. Overall, I estimate we'll average over twice the page count.
2) Free stuff, additional material - roughly comparable, I'd say. AoW had its "Overload" which is roughly comparable to WotBS' Campaign Guide. WotBS has a similar sized Player's Guide, too. Both give you the maps and stuff for free as an additional download (I'm not sure if AoW gives you 1-inch scale battlemaps, though?). By the end of the series, I think WotBS will have about twice the free stuff that AoW had.
3) Format - AoW is a series of magazine articles. WotBS you get options: PDF versions, softcover versions, and, at the end of the series, a hardcover compiled version.
3a) Cost - with a wotBS subscription, you get 12 adventures for $34.99. Compared to 1 year's Dungeon subscription (in which you get other adventures). Cost per page ratio? Not sure.
4) External support - WotBS will have associated novels, additional products, etc.
5) Flavour - as mentioned WotBS is a lot less dungeon-crawly. There are dungeons to crawl, of course.
6) WotBS supports EN World! Yay!
AoW is damn good, though. We're enjoying it immensely.