Best is a terrible thing to think of. Like any piece of audio equipment, system synergy matters far more than anything else. I personally like the Playback in my Canor System with Wilson Benesch speakers. If I switch to VAC, I think the Helios is better. Something about VAC Master preamp and the Playback DAC don’t work together. Almost like the combination is too much of a good thing.
The Weiss is cleaner and a touch colder than the MPD-8. Exactly what you would expect from an ESS based DAC. The crosstalk DSP though adds an immense amount of depth to the image and is awesome.
The Playback is warmer and sweeter. When I swapped in Westminster REI amps, it was the only DAC I really loved with those. It is also insanely good with DSD.
You have to consider the rest of the system. There is a best for you and your system and that can and should be very different from person to person.