Differences:
* Their site says they've funded over 800 companies, which is absolutely absurd in the few short years they've been around. A lot of venture funds won't do that many deals in their entire lifetime, let alone in a few years.
* They do a lot of International deals (in 40+ countries). Most other VC funds are skeptical of (and often avoid) investments outside of Silicon Valley, let alone outside the United States.
* My own interpretation is that 500 Startups also focuses on things that generate revenue quickly, and not so much trying to find the next Facebook.
* And then there's Dave McClure. If you know who he is, this bullet point needs no explanation.
When I asked, Khailee Ng told me they used that as a filter (presumably instead of "only warm intros" and/or associates binning thousands of cold pitches). I thought it was a neat idea, especially since the industry does this unofficially anyway (http://paulgraham.com/fr.html - "Avoid investors who don't lead" - obviously 500 Startups is an exception thanks to their brand and network).
Reference: http://25iq.com/2013/01/16/charlie-munger-on-investment-conc...
http://robgo.org/2013/10/21/decision-making-speed-of-big-fun...
https://twitter.com/trengriffin/status/264789822982471680
https://twitter.com/sama/status/458094667972624384
That said, in the end, real performance trumps everything.