When I was shopping, the features were a big factor in choosing the Einstein in addition to the price. Of course, the $4k pricetag that the bigger Diezels command is a very dear price to me, but believe it when people say that the 50w Einstein is not an amp you 'settle for'. The overall size and familiarity of the way the amp works is very appealing to me as a musician that still lugs around and sets his own gear up. Sometimes feature-laden amps are not what people really need, and Diezel really hit that spot with the Einstein.
What i love about all of the amps is how well they perform at such low volumes, as on stage, it's not always the prerogative to crank your guitar volume. Tone-wise, I've had the privilege of playing through all of them aside from the Schmidt, as Ultrasoundrehearsal in NYC had the Herbert to demo and the studio i used to work at had a VH4 as the go-to amplifier for most projects. All of the modes on the Einstein are a pretty good representation of Diezel's approach to guitar tone. The tone palette is very similar to the VH4, obviously the VH4 has 4 independent channels. What you've read overall is pretty spot on - the Mega mode on Einsteins being very similar to the 3rd channel on the VH4 that everyone's so crazy about. I personally like the way the clean mode on the 50w Einstein has more of a tendency to get saturated. ... the 50w clean mode has more of a British Voxy/Hiwatty feel to it whereas Ch1 VH4 is more pristine and even more 'bubbly' - hard to really pin down on what kind of voicing it is more like, as Diezel's EQs are super intuitive and easy to dial in. I've only started to get used to how to balance Ch1 and 2 volumes on my Einstein, but the 2nd channel has a great feel to it - it has the violin like sustain of a phat fuzz pedal but it retains the tightness that a hot-rodded Marshall should have.
Overall, I prefer the feel of a 50w amp over a 100w. I can appreciate how full the sound must feel onstage with a VH4 halfstack, but the way my Einstein reacts to my playing dynamics is more important to me at this point, as well as the aforementioned portability. Most venues are mic'd and even though i run a small setup (50w through Diezel 1x12), it sounds huge enough - guitar players in the audience are usually very surprised with how big that setup can sound, even unmic'd! It's just super easy to get a good live level without feeling like I'm holding the amp back live 50w sits in the mix just enough, and there also is the extra push that the Master volume II gives you. Excellent job with that amp, no doubt about it!
EDIT: Pedal wise, it excels just as much. I recommend running delays and fx you dont want the preamp gain to muddy up in the serial loop. The dimensionality of the amp in addition with a good delay unit like the Eventide Timefactor really will change your views on plugging everything straight in. Boosts and other types of gain multiplies how versatile the amp is. In addition to pegging the front end with a RMC Compressor (Adds just the right amount of breakup and modifies the attack of the guitar beautifully), I have a BD2 set for a light crunch and boost (think large Fender-ish breakup). Going into
the BD2 is the EQD Tone Reaper, the Tonebender being my favorite flavor of fuzz. It has a lot of volume and sustain on tap, so its especially good for solos straight into the clean channel, but the gain is huge without getting too flabby. I look forward to recording some fizzy fuzz overdubs with it somewhere, but I especially love the phat, harmonically rich David Gilmour-ish tone that it adds to leads. The preamp on the Einstein just brings out the best in gain pedals if you use your ears right.
