used MR816x or UR824??

From what I'm able to gather, the differences between these interfaces are



UR824: Includes extra ADAT In/Out, Morph Channel Strip/Amp Sims, USB



MR816x: Firewire, Quick Connect, Inserts on Ch 1 and 2





Are there any other advantages or disadvantages to any of these interfaces that I'm missing?



Is one more stable (drivers)?



Will the firewire offer better performance vs USB?



Are Morph Channel Strip/Amp Sims worth the extra money?



If the UR824 doesn't offer any other advantages to the MR816, the MR816 can be found cheaper used, so I'm kind of leaning that way, but I'd hate to make an uninformed decision.



Thanks all!

used MR816x or UR824??