Don't know if this will help, but I jumped up and did a comparison on my 5150 mk1 and my 6505+.
Used identical settings, both amps have identical Ruby 6l6s, and both have identical preamp tubes, being identical JJs and Electro Harmonix. They were set up like this .............
5150mk1 preamp tubes from left to right as you look at them
jj, eh, eh, jj, jj.
6505+ preamp tubes from left to right as you look at them, (remembering that the 6505+ has 1 more preamp tube than the 5150mk1).
jj, eh, eh, jj, jj, jj.
So mostly identical in every way, including the settings. (maxon 808 was used also).
Were they identical sounding? Well........ No. Not exactly. To me the tone is so close, hell, may even be identical, but the thickness was different. The + didn't have the gain output of the 5150, it was as if you could use the 5150 for dual tracking and as though the + was better suited for quadtracking. But overall apart from the amount of gain, I noticed fuck all difference.
I am happy to jam with the 5150 (loud levels), with the gain on 3, where I like to have the + at around 6 on the gain. As for being more mid voiced than the 5150, I couldn't here that. Now my XXX on the other hand ...........................