We looked at both shows, but no-starter on TC50 is that you can't have any public exposure before the event. This seems pretty silly, in my opinion. Most decent startups should have exposure before a singular event. Banking on entry into one event is a poor decision (more foolish is banking on winning the competition, as that's where 99% of the publicity goes).

DEMO has less stringent requirements when it comes to the amount of publicity a startup has before the event, which, in my opinion, allows companies that aren't sitting on their butts when it comes to marketing have a nice big event at which to launch.

Edit: I should also note that I've had one group of friends go to DEMO, and one get into the TC50 Demo Pit. The former got a ton of exposure and new users. The latter got no benefit in terms of attracting users. Granted, this is a minimal sample size.