Among other things: One, wepay isn't international. Two, you have to send users off your site to use it. Three, you can't plug in your own credit card processing if you use wepay (you have to use theirs).

Additionally, their api doesn't provide the tools for the collaboration side of things (messaging, invites, sharing, comments/nested comments, reward tiers, tilting mechanism, etc). Think of this api as a layer above credit card processing (so you get to choose whichever processor you like or already use, thus not disrupting your current flow of funds and you get to keep the branding/UI/UX, the users, the user data, and the credit card processing data, etc - all important things if you're, say, hotels.com).

(disclosure: I'm one of the crowdtilt founders)

It's similar to Wepay's except with the use of Wepay's API you're tied to their gateway and thus their rates as well. With this you'll have your choice of payment gateway (Stripe, etc) while also being able to use the features you love for Wepay, essentially meaning you should be able to get the best rates possible as well as crowdfund the things you like.

Not necessarily "better" really just a different animal altogether