I demoed the MC and then bought an MCII. IMO the MC that I demoed was a little bright on the rhythm channel. This made it hard for me to get the two channels to balance out for what I wanted. I talked to Rick about this and he said he reduced the highs in the rhythm channel so the MCII and the newer MCs are not as bright as the one I tried. If that is the case, then I would "guess" that there is no real tonal differences between the two now if they were dialed in the same way. If you want the brighter rhythm channel Rick will make the amp that way for you as some people still like that better. I didn't notice any real difference in the lead channel tone between the two amps. The MCII "may" have more gain but I can't verify this as I didn't have the two amps at the same time. Both amps can now be ordered with effects loops.
However, the MCII has a gain for the rhythm channel as well as a bright control on the back. With these two controls (and the changes to the rhythm channel I mentioned above) I found it MUCH easier to get the two channels to balance out on the MCII.