Well, to answer my own question, having owned them both. I prefer the Meitner MA3 slightly over the Bricasti M3 in my system.
I own the MA3 and owned the M3 for a short while before moving on from it. I also prefer the MA3, and by a large margin in my case/system.
I liked the M3, but it didn't blow me away. I replaced it with a Mojo Audio R2R DAC that I much preferred, but it did give up some detail/resolution (and a very nice black background) compared to the more modern sounding M3. I much preferred the very relaxed sound and natural tone of the Mojo Audio.
I then heard the MA3 and for me it has the natural sound (and no fatigue) of the R2R DAC but with much more detail retrieval like the M3. Kind of a best of both worlds for me, detailed (but not hyper detailed) with that natural sound one gets from a good NOS R2R DAC.
I also agree one needs to listen to these DACs themselves in their own system. Both offer good value at their used prices, so you should be able to re-sell either if it doesn't float your boat...
I have a Weiss 205 incoming, that will be interesting to compare to the much $$ MA3. I'm guessing it will sound more like the M3, but time will tell.