I would think if you're using ableton in a live setting then latency would be a big concern. My understanding was the USB interfaces tend to have more latency problems, but I could be wrong. My only experience with USB equipment have been the mbox and mbox 2 and they were both pretty latent for live monitoring. We've been using a little tascam fireone for our ableton setup and it works ok, but its only got two ins and two outs, so depending on what all you'll be using ableton for you might think about that as well.