I own both the M7 / Yggdrasil.
I actually find the M7 quite a bit brighter than my Yggy with stax.
When I A/B the two dacs, I used a Kgsshv Carbon + Sr-009.
I was using DI-2014 HDMI I2S to feed the M7, and standard USB gen3 to feed the Yggdrasil.
The M7 was so bright when using the Sr-009, it's actually fatiguing to listen to. On the other side, the Yggy has a more rounded sound (in my comparison). The yggy is 100% the better match for me, in my chain.
Although, like most I wouldn't consider the M7 bright. I used it with my HD800 for a long time, and always found the M7 more liquid, velvety, then my other Delta-Sigma dacs.
It's so hard to just say X v.s. Y in the DAC realm. There is the amp/headphone to consider. There is all the offboard junk when using a DAC to consider (I know some people spend more on offboard equipment then the actual $2k dac).