Let me clarify what I stated..... The Mark III lead channel may be better than the Mark V. I would not necessarily say it is better than that of the JP-2C. So far that has become the standard to which I would compare my other amps, including what memory I may have about the other's I had in my lifetime. I never had a Mark IIC+ so that may change if I had one. However, that being said, before the JP-2C came along, it was the Mark III that I held as a standard tone reference. It is too bad I sold it before I got the Mark V as it would have been great to get a comparison. I did have the Mark IVb (wide body version) at the same time I had the Mark III. Ease of use and overall tone was preferred over having to look up settings to dial in various characteristics with the Mark III so reason that sold first. At the time I sold the amp I was done with playing all together an had no interest to continue. Just after selling the Mark III I had a life changing event such that the guitar was my escape from reality so I got back into it and have not stopped since. Why I stopped in the first place was due to an injury that caused difficulty to play (pain). I was able to push back the pain to play and now I no longer struggle but have lost most of what I was able to do in the past prior to the injury. The Mark III was one amp that once set you leave it there as it is easy to loose that tone you love and may be time consuming to get back especially if you forgot what was set up. Reason why many manuals have templates included showing blank dials and such. This all predates the digital campers that are common in most if not all cell phones. Take a picture and label it. At least the Mark III had numbers on the control dial to reference (not that it really means anything).
In hindsight, the JP-2C is a modern version of the amp that created the big stir in the industry (the limited number of Mark IIC+ which were basically customized and tweaked amps). The Mark III series does share some common ground to the IIC+ and some versions were closer than others to the original circuit. The Blue stripe was an improvement and closer represents the power supply section of the IIC+ and is said to be much brighter than the other iterations (stipe colors in order of release: black, purple, red, blue, green). I am sure there is a recorded historic development of the Mark Series amps online....