Okay, I've been playing around for a while now and first impressions compared to my Engl 2x12" Vintage: The Mesa is slightly smoother with a bit more bass and weight to the tone. Otherwise they're quite similar. When recorded, the Mesa seems to have a bit more midrange and less treble when recorded from roughly the same location on a speaker with the same SM57. But the overall response to playing and so on are pretty much the same on both cabs.
Here's a quick first clip I recorded, Engl Powerball -> Mesa -> SM57 -> Fireface 400 -> Cubase
http://koti.mbnet.fi/juhau/mesa.mp3
Just a highpass and small notch at ~800 Hz. There's two different mic locations in the clip, the first one is a bit further away and more to the side of center, and the second one is almost touching the cloth near-center.
Here's two pics too: