Robert S. said:
The Mark series of amps are all very different in tone and in gain. They really are quite different from each other and it's hard to compare them really. The gain stages are all different, the mids placement is different and the clean channels all have their own unique character as well. Saying that the Mark III is better than a Mark I is really very subjective, as they are completely different amps.
I've played Rectos, Rectoverbs, Marks, a Blue Angel and the new Lonestar receintly and they are all great sounding amps. The Lonestar in particular is a killer sounding amp with more than enough gain, killer clean tones and a range of pushed tones that makes it a great combo for almost any situation.
No one likes everything by any one maker but if you can't find a Mesa that works for a style you haven't looked hard enough. They really do have quite a line up curently and I can't think of another amp maker out there that covers as many bases tonally as Mesa with simular build quality and reliability.