As a guy who has used both products and made some great customized applications with both, I can tell you that the WebAssist extensions actually offer you much more possibility because of the way they operate. The ADDT engines are so limited by the transaction protocol that it would drive me mad sometimes.
I get it though... for simple quick CMS creation, the ADDT work flow is a little simpler and faster. But, if you plan on making truly customized applications with various options and sub-applications, the WA extensions are much easier to manipulate. There is a little learning curve, though, with the WA stuff.