Just as a side note, I played the Pony for years as Monmouth county is my home county.
I played on Mesa amps from 1974 through 1989, and they got to be so complicated to dial in, that I gave up on them, and went to Marshall amps for awhile until I heard about Diezel amps.
The wiring in Mesa amps is so complicated due to all the options it has, that the tone becomes degraded after having to go through all the wiring options. Also, Mesa uses cascading distortion by using channel one to boost the next channel and so on. Any change made to any channel affects the saturation and voicing dialed in on the other channels. Jim Marshall was correct in saying that the purer the circuit the better the tone.
Diezel amps are all this way. Four independant preamps. You can dial them in blindfolded. I tried to help a friend of mine dial in his MK IV. It took us 4 hours to get all the channels to where each sounded as good as they were going to get. Then I let him plug into my Diezel. I had used it the night before and the dials were still set from that job. He turned it on and immediately said "That is the sound I want from my Mesa!" I told him to sell the Mesa and buy a Diezel.
Yes, Mesa has it's sound and it is unique, but the constant tweaking drove me crazy on those amps. After the MK II B, it was all downhill for me with that company. The amps became way to finicky and lost the simplicity of dialing in tones they had with the MK II B. The MKII C+ was a horror show to get all channels to have the tone I wanted. Also, the saturation was gritty and hard on my ears no matter how I dialed everything in.
Not so with a Diezel. The Diezel sound, to me, is bigger, wider, fatter and can be dialed in easily to brighten or darken up the amp to taste. The saturation has more roar and vocal quality to its sound.
Forget the cost of the amps in question. You will be spending far too much time tweaking and re-tweaking the Mesa. Is your time more valuable spending all that time dialing in the tones, or would you rather turn the amp on, dial in the sound immediately and begin to enjoy playing through it?
You decide. Good luck in making your decision.