TechStars could also judge their applicants on a criteria different from Y Combinator and catch good startups where YC might not.
The word on the street is that most startups, however, wouldn't choose TechStars over Y Combinator. First, the initial investment is lower. Second, they aren't original nor do they have the reputation that Paul does. In the end, though, it all comes down to which program maximizes success for startups. For that, David had this to say in an e-mail "Our investors have funded several hundred companies over the years, far more than Y Combinator has done. Y Combinator has Reddit to point out. Our founders point at Newsgator, Technorati, Feedburner, Dogster, and tons more as examples of our past experience."
I don't think anyone hates TechStars, but startup's would have had more respect for them if they had at least taken Paul's permission for rewording and copy-pasting the questions :)