I own both of these heads and these are my observations of each amp:
Wizard MC-I(hand-wired with updated gain mods) Mercury C spec transformer, bulit like a tank:
Gain Channel(3 levels of gain via push/pull
Gain 1: (Angus & Gibbons) Very sweet, open, and articulate with plenty of bottom and top. Very AC/DC/old Marshall type of tone.
Gain 2: Added gain with the cut of a Hiwatt while retaining some of the sag of older Marshalls. Smoothest mode and darker than Gain 1 & 3.
Gain 3: (Sykes & Lynch) Balls out distortion that can get very heavy. I find this tone/mode very unique because even with the additional tons of gain the Wizard still retains that old Marshall/Hiwatt clarity and punch. Bottom stays tight as well.
Clean channel: The clean is good but not great. The built-in boost it really kicks up the volume with mild breakup. Again, sounds like an old Marshall set clean to my ears.
Friedman BE(updated specs as of 1/13) I think the transformers are Heyboer:
Gain Channel: The Friedman has both the BE & HBE as well as the C45, Saturation, Fat, & VH switch.
BE: (Steve Stevens & EVH) The BE is a perfect Marshall type amp with Dave's unique voicing. To my ears it's the perfect modded Marshall with a very special mid-range quality. The VH switch increases the top and bottom slightly and the C45 makes the tone a bit more round/modern with more gain.
HBE: Pretty much like adding an OD pedal to the BE channel. Slightly more bottom and smoother than the BE mode. Great note articulation/clarity and tons of sustain.
Clean Channel: The clean on my BE is incredible and doesn't get enough credit. It's a damn near perfect IMHO with the option to get dark(middle toggle), Fender/Vox(left toggle), or Fender with a boost(right toggle).
Things I don't like about each of these amps:
The Wizard can get harsh with the high-end at lower volumes.
I don't dig the BE's effects loop. Mine is noisey. I run a line-out so it's no big deal but the loop could be better IMHO.
Just like any other amp, it all comes down to the player's taste, style and preference.
Here are a few videos of my Wizard(Mode-3 Highest Gain) and Friedman (BE with no Saturation switch
My Wizard comes in at 3:45:
Happy amp hunting Bro!