My friend has a Quatafire which is actually rather nice. The pres on their aren't bad.
The RME unit I bet would sound better. My previous experience with their quad mic pre was very nice and I imagine the pres on their fireface will be similar.
RME drivers have a reputation for being extremely stable.
I personally think the routing in the ESI cards to be excellent and easier to work than pretty much any other card out there. If you demand ultimate multi-client routing between applications, the ESI will do it.
Pure sound quality, I'm guessing the Fireface, just based on RME reputation.
