DAC Chips

The DAC chip is only a part of the greater whole. In other words, you should look at other factors when doing a comparison because every part of the DAC could in some way, determine the sonic signature of that component. Many people want to say that they prefer one DAC chip over another but what matters is how that chip is implemented. Ten companies could build a DAC with the exact same DAC chip, yet they would all sound different.

Absolutely right Mr goofy foot

Both chips in PRO version are 2x8 channels.  My Benchmark DAC3 sums them by 4 and uses dual differential outputs.  That way they use all 16 channels.  9038PRO according to links provided by George, has dynamic range of 140dB, but it is in mono mode (8 summing?), while for 129dB in 9028PRO mode is not specified.  They differ very little in THD + Noise (-122dB vs -120dB) and that's perhaps why Benchmark chose cheaper 9028PRO for DAC3.  

My Ayre uses an ESS DAC chip also.

I also think that what @goofyfoot said is an important point. It is as silly to judge a DAC by its chipset as by the thickness of the front panel.