The ESI is class compliant, and the class compliant driver is NOT multi-client, afaik
I’d stick with MOTU but be extra careful with which generation you pick up. I just picked up a used USB MTP AV to replace my parallel MTP AV and Express XT interfaces but now need to track down a ROM chip to get it working in win XP.
Also if you buy a used MOTU chances are you’ll probably want to replace the battery – lots of people sell their "dead" interfaces and the only thing wrong with them is the battery is dead or dying. 
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