Disclosure: I am the Chief Architect for Universal Audio. That said, I'm not in sales, and am not trying to sell you on Apollo; just trying to answer some of these questions. Hopefully that is OK with the forum rules.
I've read through this thread and there are two main themes here:
1) How does UA measure their devices and is it just marketing?
2) What is the reason to integrate DSP into an audio interface?
If I could answer briefly...
1) We have a very talented team of scientists and engineers that are very proud of the audio performance, both analog and digital, we've been able to squeeze out of the parts we're using. That measurement data is coming from Engineers and is certainly not intended to be misleading. I will ask about whether we are strictly measuring to AES-17. I know we have to tweak out our AP units to be able to measure our performance as we exceed the auto-ranging performance of the AP.
2) In addition to just wanting to make a great analog/digital interface, we do have a long history in digitally modeling classic studio gear. There are a few advantages of integrating that into an interface. The first is that all of our modeling plugins have the ability to be truly voltage calibrated. If you use a typical audio plugin in a DAW, you don't know what voltage a particular sample value is because every audio interface has a different 0dBFS to Volts reference point. Since we're integrated, our effects know this calibration and can behave exactly like the real hardware. The second is audio latency through the effects themselves. In a professional recording environment, a vocalist can often detect latency in their headphones greater than 3mSec. That is difficult to do through the host computer processing. Doing it in DSP, on device, we can deliver effect processed sound to headphones of sub 2mSec. The last one I wanted to mention has to do with a unique feature of Apollo. Our unison mic preamps have analog circuitry on the front end that allows us to alter the input impedance of the channel to match that of a physical piece of gear. Some microphones are very sensitive to the input impedance of the preamp that they are plugged into. When we model a mic preamp in our devices, we physically change the analog into to match the modeled gear, thus interacting with the microphone in the same way as the real mic preamp would have.
One more thing to consider when evaluating these devices is the analog circuitry on the outputs. We take this very seriously. A good example is headphone amps. You can have a great DAC, but if you listen on headphones, and your interface can't drive them well, it's not going to sound good.
Dave