I think the most important distinction here is, how many simultaneous channels of input do you need? If two analog ins is enough for all you want, get the Audiophile. If four would be better, get the Midiman MIDISport and the Delta 44.
Also, do you have any gear with S/PDIF digital out? If so, or if you expect to in the future (for example, if you were to get a Johnson J Station as a guitar modeling device), the Delta 44 has no digital input, and 4 analog inputs are what you want, it would behoove you to spend the extra $50 street to get the Delta 66. But if two analog ins are enough, the Audiophile has an S/PDIF port.
As to the USB questions, well, supposedly USB MIDI timing is not all it could be, and I guess someone with critical MIDI needs, triggering lots of synths and very sensitive to the timing discrepancies (which are on the order of 3-10 milliseconds) might find them to be a little off. But for me, just using mine to capture MIDI input from my keyboard or drum pad controller, and occasionally for editing parameters on my POD, I have never noticed any slop at all.
