I have the prior gen D-A, Ult and 105 pedals. 105 to Ultegra is massive in look, feel and bearing smoothness.
Ult to D-A is somewhat noticed for bearing feel in hand. The D-A feels like perfection despite MANY unknown hours of use on my trainer bike. But for the price difference, this is the epitome of “marginal gains” IMO with very few people able to appreciate let alone detect the deltas when on the bike.
I got the D-A to match a bike with R9000 and only got both via shop discount. Even with that discount, the price jump to D-A is just short of insane for me. Much like the other top vs 1 tier down Shim stuff, the D-A / XTR level is hard to justify in real numbers, but makes perfect sense if that is what you want (aka the BEST).