The D8000pro is closer to diffuse field tuning where as the standard D8000 is closer to the harmon curve tuning.
For me, owner of both, the PRO model is a significant upgrade, so much so that I don't know if the standard edition can hit my top 10 whereas the pro is in my top 3.
For me out of any headphone in the market the D8000pro gives the least intrusive window to the music the engineer wanted you to hear. In terms of how wide the soundstage is, how intimate the recording is, the warmth, the scale, the feel.
Everything seems very accurate, I also own Spendor D7.2 floorstanders and the ATC SCM25 as 2 extremely high end revealing speakers to compare and contrast my headphones too.
The D8000pro is amazing, BUT, it doesnt colour, flavour, enhance or change anything from the original source. So dont expect anything to be flattered. If its beautifully recorded you will hear every aspect of that beauty.
The other advantage here is that you can then "flavor" your experience with amplification choice (eg tube ampes).
For me the Susvara can compete BUT it really requires an absolute monster of an amplifier to truly shine.
The Abys phi-TC beats it out on dynamics, impact, soundstage, scale and bass BUT isnt quite as delicate and refined.
The Utopia beats everything with its unrivaled ability to provide the listener with true depth from a headphone.