My blog’s visitors certainly could tell the difference: I’ve been blogging much more frequently. And that’s really the only useful test of a blogging platform. Most of us don’t buy a car because we enjoy tinkering with cars; we buy them because we want to get somewhere.
Years of building and maintaining my WordPress blog have resulted in my learning a lot about WordPress and getting a lot of grease under my fingernails. Weeks of using Posterous has resulted in a media-rich blog with several posts per week. Tell me which service is more powerful.