HE-4 doesn't have the richest vocals itself though...
It is indeed better for metal and more aggressive rock genres than the MD though.
That is, assuming you have an incredibly powerful amp that can utilize the HE-4 to it's fullest. That thing ain't no joke when it comes to amping requirements. I'd say at LEAST the Lyr.
You don't want extra lushness (= distortion) for an already heavily distorted sound (metal/hard-rock). Otherwise it becomes a happy mess!
The HE-4 have clean mids, which is perfect for those genre.
IMO, of course.