Maddogs are more balanced than the he400 which puts some emphasis on the bass. But the MD still has that silky smooth ortho sound. MD wins on mids. The mids are some of the best I've heard. The treble gives wonderful detail but never sounds harsh or strident.
Maddogs will isolate wonderfully while the he400 will sound like mini speakers to everyone in the room. The he400 amps easier but is not as comfortable as the MD. They are both great hp's...just depends on what you're after.