I'd highly recommend the 750's, can drive anything, used by Nudell, and reliable as anything. BTW, have owned 201's.
Is this a trick question, or an attemp at humor?! The Atma-sphere MA MK II.2 (now upgraded to the MK II.3) and the VTL-750 are in two different leagues!!! Comparing the Atma-sphere to the VTL is like comparing a Porsche to a Yugo! If you check out the specs, design phylosophy and circuit layout, and company histories and REPUTATION, it's a "no brainer". Go with the Atma-sphere. You've been forewarned.
Mejames, if you are concerned with the 4 ohm load being driven by an OTL, you should look into "The Zero". It is an autoformer that allows the amp to "see" an 8 or 16 ohm load. Some would say that putting a transformer between an OTL amp and a speaker is defeating the purpose, but I disagree.
Talk to Ralph Karsten about it (Atma-Sphere president), he is VERY knowledgable and forthcoming. Basically, Ralph will tell you that ANY tube amp (OTL or transformer coupled) could benefit from using an autoformer if asked to drive loads less than 8 ohms. The benefit with an OTL is that since the output impedance is already rather low, the turns ratio on the autoformer is drastically reduced and consequently, the autoformer can be made to a much higher quality standard with less cost.
I love my MA1 MkII.2's driving my Kharma's. They are in a completely different league compared to my Manley Ref 250's I used to own. In comparison, the Manley was more like a musical instrument, making it's own music and clouding the musical tapestry. The Atma-Sphere is a true musical transducer, a grain free, veil free, distortion free reproducer of the music it is fed.