Jason R.,
I can only offer advice regarding the Allen & Heath ZED 14. I have been very pleased with mine... as an analog mixer.
Thankfully, I purchased it with the main purpose of using it
as a mixer, with the thought that it would be a pleasant coincidence if the USB interface met my standards. I'm sorry to say it did not.
As a mixer, it would be very difficult to find something comparable for the same price. Its USB interface left a lot to be desired.
Once I discovered there was no ASIO driver written for the ZED, and I would have to either rely on the Windows generic USB audio driver or try using ASIO4ALL drivers, I was bummed. But I gave it a chance, and tried every possible configuration (seriously). The interface WORKED, but the noise floor - of the USB interface, not the mixer circuitry - was too high for my use. I got a lower floor from a ("low-end") Alesis io2 Express box than I was ever able to get from the ZED.
I eventually bought a Focusrite Scarlett 8i6 as my interface (wonderful piece of kit), and run the output of the ZED14 into the line inputs of the 8i6. It works great for my purposes, but it sounds as though a similar scenario might not work as well for you.
SO... while I would highly recommend the ZED 14 as a pro-quality compact mixer (6 excellent mic preamps, smooth long-throw faders, 3-band swept-mid EQ, etc.), if it is crucial that it double as a primary interface, I would disqualify it.
Cheers!
Joel