The BAT is slightly dark-sounding, hard to describe but not as airy or sparkling as most amps. A great choice if your speakers or upstream components sound a little too bright. The ML 27.5 is a great amp and thought by many to be superior to their newer stuff. ML's seem to err a little to the "refined" side of things to my ears, almost too smooth. But again, many people love them for just that reason. YMMV.