I've done two slow ones and one live draft so far. I've also seen some results from other drafts. It does appear that either the competition is tougher in the slow drafts or it helps the competitors having extra time to do research to make their picks. In other words, the slow drafts have been a lot tighter than the live ones from what I've seen. So, if you're really organized and ready to draft you may be able to find easier money in the live ones. Just my preliminary observations so far though.
It's a lot of fun but the vig is a little steep for some ($2K payoff on $2,640 invested, 76% payback if you take the cash). If you take the WCOFF package, the payoff is much better (over 95% assuming you're going to stay at the host hotel) but you have to wait an entire year (technically) to get paid off for it and that's assuming you're available to draft the following year in the main event in Las Vegas or Atlantic City.