TED talks are getting to be a counter-signal of credibility.
The talks I've seen out of TEDx tend to be more "this is interesting" rather than "this is 100% the truth about ____". I think most TEDx events take themselves less seriously, which results in fewer speakers that think they are the end-all-be-all of some topic. Where as TED events seem to try to get the "foremost expert on ____", even if the entire area of _____ is mostly quackery.
Though really I think the pompousness is proportional to size and has (almost) nothing to do with TED vs TEDx. Anecdotally, the fairly large TEDxGlasgow had a lot more wankiness than the quite small TEDxUbud.