Alright - FWIW I did this comparison blindly as well, just as you all. I'll start telling people privately which is which shortly. Here's my take:
A Comments
Overall punchier than B, I think contributing to the in-your-face feeling RobC mentions. Highs kinda jumped out at me, but I found them a bit spitty and a little harsh, fatiguing to me after a while. I don't hear as smooth a transition from highs into mids as I do on B. Mids and vocals more up front, but again not as defined/detailed and there's something - maybe something missing? - here in the low mids resulting in a stridency I found fatiguing. More prominent low end but fuzzier and not as rich and defined as B.
B Comments
Overall smoother and richer, more detailed, more integrated across the range from high to low, if that makes sense . Crisp, clean, smooth highs - they don't stand out nearly as much to me as on A. Meatier/fuller mids and vocals, although not as up front as A. Lows again not as prominent, but tighter, smoother, more detailed, somehow...broader and deeper.
Individual Responses
RobC - I hear you on the in-your-face sense, the up-front feeling on source A.
Daryan/Chase - we definitely have different playback systems and/or ears! For the most part, I hear things differently than you describe them, though it may easily be chalked up to the difficulty of translating what our ears hear into the written word.
BCostigan - I think we're in agreement, here.
Tube - I'd love to hear this comp with DPAs/AKGs, too - maybe I can hook up with someone in the Cleveland/Columbus/Pittsburgh areas to try it out. When you say the Schoeps boom hurts the UA5 source, which do you mean: A or B?
Jonny - looks like we're in the minority here on preferring B over A.
STL-Taper - I definitely agree on what you're hearing in the low mids on B (or not hearing in the low mids on A), but not so much on the muddiness of the low end.
Bottom Line For Me
Personally, I prefer B. While I appreciated the punchy, in-your-face feeling of A initially, I found the - to me - exaggerated highs and lows fatiguing and really enjoyed listening much more to the richer, smoother sound of B.
Playback Gear
PC >
Waveterminal 2496 >
Airhead 'phone amp >
AKG K501s headphones
and
Toshiba SD-2900 (cheapo DVD/CD player with digi-out) >
Sony E9000ES (basically acting as DAC) >
Rotel RTC-950AX preamp >
Adcom GFA-555 power amp >
Magnepan MMGs / Pinnacle Babyboomer sub