Mike --
the Dart was similar to the FM in the mid to upper mid range. In the high frequencies, the FM showed more energy. Note that where details of the music were concerned, the Dart did not require you to "strain your ears" i.e. the Dart+Dart was not musically lossy or lacked homogeneity. Cymbals for example had more energy and slower decay (i.e. they were perceptibly present longer) with FM.
Also please note that the speakers were adequately set-up and the amplfication homogenious enough in both cases so there where no aberrations such as, the percussion being in front of the violins in an orchestra, for example...
Riaa: haven't made the comparison, unfortunately. The FM (122 in this case) has 2 user user-controlled de-emphasis pots in front which allow versatility -- but would probably complicate comparisons (unless maybe if set flat on the FM?)!
Cheers