it is very important!
with the ua5 it does the analog > digital conversion, and to get analog out of it, you must go through the digital > analog conversion again, which is not anywhere near a good thing to do. this could introduce noise to your signal.
you would have to set the levels on the d7 when taking an analog signal, and on the ua5, but using the 7 pin and taking the digital signal you would only have to change the levels on the ua5.
and taking a digi signal on the d7, im assuming it has decent levels on the display, you could use the levels on the d7 for the whole rig. sonce we all know the level meters on the jb3 suck!
buy a 7 pin! but dont buy a core sound 7 pin, no matter how cheap it is!