I do think is Steve Blank is more legit, but not because he did multiple companies - if you worked on several venture-backed companies throughout your life but they all went nowhere, you must suck as an entrepreneur. I just looked up Epiphany and this answers my question, he founded it, did $71.5M in revenue, and it IPO'd, so Blank definitely knows what he's talking about: http://en.wikipedia.org/wiki/Epiphany,_Inc.
IMVU on the other thand had good traction and Eric Ries was VP of Engineering there, but what's happened to it since? Just looking it up on crunchbase: http://www.crunchbase.com/company/imvu - no big exit/big numbers or anything special like Epiphany?
And here's his LinkedIn profile: http://www.linkedin.com/in/eries - it just doesn't show any blockbuster results as an entrepreneur, just a lot of advising/marketing/blogging.
http://en.wikipedia.org/wiki/IMVU
http://en.wikipedia.org/wiki/Steve_Blank
They are both the real deal - especially Steve Blank, who did multiple companies.