If you can avoid it, don't force yourself into this dichotomy (choosing between these two brands) - there are a lot of manufacturers making a lot of units with different price, features, and and quality -- definitely check out interfaces from RME and Echo, for instance. Further, the folks who can boast of the best signal chains tend to have separate components for each of the functions I associate with an interface (preamp, A/D, D/A, clock, etc.).
I have a low end interface from Presonus (Inspire 1394) and a mid-range unit from MOTU (traveler), and use them both on macs. I'm not aware that I've experienced any meanginful latency or software problems with either of them. I recently picked up a Digi 001 for a total of about $50 (got the breakout box and card in different places), and boy howdy, on XP there's some serious latency. But whatever.
The Inspire is totally entry level, and the pres are pretty noisy once you turn up the gain about halfway -- nevertheless, I got some good tracks with a high sensitivity mic and the gain set low (and with digital recording, low gain is good, since you can always boost it digitally). The MOTU pres were much higher gain and quieter, but didn't have a great sound, and one of them went bad. I sent the unit (my second, after getting one replacement from MOTU) to Black Lion Audio, who modified the analog stages in it, and I also picked up their microclock - since then, I couldn't be happier with it (at least I don't think so
) And I still don't feel qualified to opine on which of the two companies is better or worse, having experience only with these two interfaces.
Make sure to read up on the other alternatives.
