A bit of perspective about effects pedals
One thing to remember about all these pedals, Boss included, is that so much of peoples' opinions about these techno devices are subjective, and based sometimes on limited knowledge. Why do I say this?
I have been an enthusiast of the Boss Metal Zone for 15 years, however I ran into a dispute with another guitar player a few years back, who swore the MT-2 Metal Zone was just junk. He proceeded to hook up his MT-2 and put all the controls on 12 noon. (Hint: the Metal Zone, as does the MD-2 Mega Distortion, has a parametric equalizer that allows you to custom contour your tones and parameters... you MUST know how they work or else they sound terrible.) The way he had it set, it DID sound terrible because he took no advantage of the great parametric EQ. It had no bass, too much treble, no midrange, it was miserable.
So, my recommendation is learn how parametric equalizers work, FIRST before judging FX gear. I usually set my bass for around noon to 2pm, my treble around 9-10 AM, and the midrange for about 2 pm for the level of midrange, and 2pm for the level of midrange so it is potent but not overwhelming. Same for distortion. Distortion can be overemphasized, or unexploited, both leading to tonal misery.
On the MD-2 I like the distortion set to 9 am to noon generally, so you really come across powerful but almost clean. If you crank distortion to 3 to 4 pm, your tone will be so distorted it will be mush. If you set your midrange range to be low, it will cause your entire tone starting with midrange to be absent, almost non-existent..
And of course, the way to set the volume is to compare your clean volume and try toggling your distorted volume to be set equal to, or just slightly higher than your clean rhythm sound, so your leads don;t overwhelm the listener or audience but does stand out a little bit, (to a good bit if you really want your leads to strut out.
Without these nuances, the qualities of these good pedals from Boss (or any other brand) cannot be understood, explored, and articulated .