Had a roadster, sold it. Had a pre 500 head, wish I still had it. Currently have a first year rackmount recto that I bought from a friend who picked it up new with a matching cab, and it KILLS. There are going to be variances in amps, but pound for pound the early two channel heads and rackmounts sound better in my opinion. I also know this rackmount sounds great because I compared it with my pre 500 and it sounded better - tried to buy it from him then and he refused. Only sold it because he quit gigging and needed some money for a down payment on a house.
My amp sounds like King's X Dogman in a box. Roadster I had was a fizzy mess in comparison. Now, if you need a clean channel and two gain channels, a newer mesa may make good sense to make the compromise. I've thought about taking the Mesa rackmount 1/2 stack and running it with a Fender Twin for live, but that's too much crap for a bar gig. I prefer my VHT UL overall but the Rackto does have it's own thing going on.
Saw a few interesting posts comparing a rackmount with the newer amp - one compared EL34s and 6L6s. Well, might want to run the same tubes, if you're into low end an EL34 isn't going to have the same amount or be as tight as a 6L6 amp. I could compare a mustang and a camaro and put all season tires on one and summer performance tires on the other - it might skew the results, yes?
Other comparison had 'same settings on the amp' which depending on the pot tapers and values could be WAYYYY off.
Want to to a valid comparison? Use the same tubes and cab, and dial in both amps to sound good, not to the same settings. Just my opinion.
Pete