From the word on the street (internet) the Fuji has crappier wheels and stem. The fame is decent but not real 'track' geometry, close though. The Pista has a little better wheels and true 'track' geo, although they are really common. Overall the Pista is a better bike for the price. I think the Fuji track is pretty ugly, and you could spraypaint (or powdercoat) the pista and it would look pretty decent (and not like every other chrome one on the street).
I have no idea about Sun Uno's.
You might want to check out www.irocycle.com as the MarkV and Angus are two of the most recommended low-end complete fixed gears. They have a nicer wheelset and arent as common as Pista's or that Fuji. As I said a couple posts ago, I'm thinkin about grabbing a White IRO Angus frame in a month or so.