Ch2/Brit with the gain wide open is comparable to Ch3/Vintage with the gain around 2/3. It is just voiced differently, with that upper midrange harmonic richness that Marshalls do so well. Also like a Marshall, diming the gain makes the feedback damn near uncontrollable. You really want to throw a pedal in front of one to make part of your gain, since...well, that is what you do with a Marshall.
If you're jonesing for a Marshall that bad, than you really want a Stiletto II. If you want a very versatile Mesa with a channel that thinks it's a Marshall, then one would do ya fine.