Hmm, didn't know of Partiful. Quick look at landing page, seems more geared to parties and more social media-y? Meetup's event listing was good as it was; well, before they started charging for you to even see who's attending.
In NY + SF, it's used for anything you might want to attend that would be organized by an individual - parties, meetups, food crawls, classes, concerts, local events, etc.