3203... Is that the one with a solid state pre and a tube power section? If so, I'm REALLY curious about that.
I'm an avowed Mesa fanboi, so take the below with a grain of salt (or don't - your call), but it's really a question of the right amp for the right situation.
By and large I don't get on with Marshalls. The JCM 800 I got to wind up once was an exception (KILLER lead tone, goddamn, I could see why that model got so popular), but their more "contemporary" sounding amps do nothing for me. Overly aggressive crunch that can't really be dialed out (I like a smoother lead tone), and more of a low-mid than a true low end.
Again, that JCM800 is a huge exception (as probably is
the JTM-45 and many of the "old school" Marshall designs). If you want an amp you can just crank up, stand back, and let roar, then they're awfully tough to beat. I'd love to have an 800 lying around for kicks and the occasional overdub, but honestly I don't have anywhere where I could really turn it up, lol.
Mesas are a
totally different animal, though. If you ignore the Rectifier series for the time being, they're mostly designed with cascading gain preamps designed to give you smooth, liquid saturation even at low volumes, and tend to emphasise depth and "chunk" over crunch. The Rectos are sort of an odd breed in that they ARE crunchier than is the normal for Mesa, but creative EQ'ing (they're the least intuitive amps I've ever played, especially the modern channel) can smooth them out quite a lot, and the power amp will do a lot, too.
Anyway, I'm sort of rambling, but they're really tailored for two different sorts of players. Guys who like a lot of "crunch" coupled with fairly tight, not overly dominant bass and a lot of low-mids tend to gravitate towards Marshalls, while guys who like searing saturation and lots of depth tend to go more towards Mesa. There's been some overlap lately - the Mode 4 and to a lesser extent, the TSL (with it's deep and mid-shift switches) was an attempt to tailor the Marshall sound towards Mesa audiences, while the Stilletto was Mesa's take on the Marshall sound.
Anyway, long story short, for me they don't because the features behind the "hype" tend to be something I want. For you, it sounds like you're more the
"plug and play" type who's more into the bare Marshall sound anyway, so it'd most likely be a waste of your money.