I like the mico a bit better however it doesn't play nice with the 680, now it has with every other digi gear I've tried. The focusrite does work with the 680. The focusrite is clean and clear where the mico is warm and punchy. I use the mico for analog into the 680 while taking the mico digi out to my backup microtracker. The focusrite goes digi into the 680.
I would bet the focusrite saffire 14 blows the ua5 away. You have to program the saffire for user settings. I did it the first time and it has maintained those settings since day one
if using the 680 I'd go with the focusrite. If not go with the mico
I think both the focusrite and the mico have better pres and converters than the stock 680.