Well, I just switched rigs (first time in years, I'd been faithful for my Nomad for so long that I figured this was "the one") so I guess I'm not in a position to say because I'm still in that euphoric new rig mode. That said...
I bought my first Mesa my sophomore year in college- it was a Rocket-44, basically a super-stripped down Mark-IV style amp, with a clean channel, a lead channel, and a switchable "contour" mode for that Mark-IV mid scoop sound. It was a great amp, but then one day I did a gig with a friend's Marshall DSL40 simply because we couldn't fit both of our amps on the small stage we were playing on, and dug how while I didn't care for the amp on its own, it seemed to hit all the frequencies just right to sound good in a mix. I'd always had toruble with rhythm/lead differentiation on the Rocket-44, too, so it sort of put the bug in my head, and eventually I sold it for a Marshall TSL-100 head.
That lasted about a year, with me digging the rhythm tones, but never being 100% happy wiith the lead sounds, until out of boredom I went down to a GC to check out some Rectifiers, since I knew a guy who was interested in trading a Triple for a TSL (probably plus cash, I forget). I didn't get on with the Recto, but just for kicks I plugged into a Nomad combo they had sitting in a corner, and just almost immediately fell in love. Straight out of the box, Channel 3 Vintage was the sort of lead tone I'd been trying to get from the Marshall ever since I bought it. I traded the TSL in two weeks later, and took that Nomad home.
I think I'm about to sell the Nomad since I'm digging the hell out of the Rectifier I just bought now that I know how to dial them in and have a Hot Plate so I can saturate the power amp, but while I'll probably continue to go from Mesa to Mesa for the rest of my playing career and maybe will grab something else every once in a while on the side, I've kind of come to realize that I'm just a huge fan of the Mesa "lead" sound, and that there's not much else there that sounds or feels the same way. It only took me four years to realize that.