I think it depends on what type of clean you're after and what type of gain.
You mentioned MEsa and Vox....the Vox part is important.... if you like the vox cleans and cruch I think you'll be happy with a Schmidt. The cleans are very vintage like and the crunch is more vintage too, less compressed, more open, I guess like a nice vox or fender amp would feel. The Schmidt also get extremely heavy, so I heavy I believe you can even play metal with the right pickups/guitar, without even having to add an OD/boost. Obviously it won't be a chugga chugga gain like the other brothers, but it'd work perfectly well for a hard rock/80's type of metal.
The Vh4 (I own one) is extremely versatile, the cleans are very sweet and with low output pickups it shines, my strat loves the VH4's clean channel. Vh4's channel 2 is the magic channel IMO, usually the VH4 is sought after because of it's incredible 3rd channel and I agree it's like nothing else out there, but channel 2 is were the magic happens if you have the right guitar (again, low out pickups) it goes from a slightly break up clean all the way to 80s marshall cruch. Channels 3 and 4 are just the tits for hard rock/metal
Einstein: is a terrific amplifier that has it's own thing going....the gain is very liquid and spongy, I loved my, I sold it because at the time I couln't keep both the VH4 and Einstein and the VH4 being the most versatile I kept it, but with the channel 1 mod it's a FANTASTIC amp.
Herbert and Hagen I haven't owned, nor played extensively, but I've heard the Hagen is just like the VH4, a monster in versatility.
if you're after the vintage cleans all the way up to rock/hard rock, I'd look into the Schmidt.
If you want more modern cleans and all the way up to brutal gain, then the other brothers.
just my @0.02
