I also was wondering about this comparison as I own the VA Beethoven Grands but am looking to upgrade. I just recently demoed the PSB Synchrony One's. Here are my findings (I'm going to be specific instead of elaborating on generalities):
Both have beautiful mid-ranges that are clear and very detailed. But the PSB has a bigger and more palpable mid-range (especially with vocals) that allows you to reach out and touch the singer. You can see into the vocal chords...hear and experience every breath, every tonal change, voice inflection.
The VA treble has more sparkle. The PSB treble is dryer. Both are equally detailed. Neither treble is as extended or airy as say the B&W diamond tweeter. But they are precise and very clear. I prefer the VA treble.
Sound presentation- The PSB has a more forward presentation and a slight emphasis in the upper mid-range. Which means (on a given song) the upper register on the piano and a high a lot/low soprano voice can tend to compete for the same space on a song. The VA has a more laid-back sound and is slightly recessed in the mids. Overall, the VA is a more "intimate" speaker. It comes across as a great bookshelf speaker but with much more bass. The PSB has a more grand, full scale sound that sounds great on orchestral music, blues and big band jazz.
The VA images better...better yet, its images are tighter within a smaller space. The PSB also images well but it captures the air and space around the images better. Ambient detail and acoustic space (the tonal characteristics of
the recording space or live venue) are more easily captured and displayed than the VA.
Soundstage width is about the same. The PSB has better soundstage height.
The VA bass does not go real deep but is extremely tight and well defined. It's also fast. The PSB bass goes very deep and anchors the music better because it has a fuller sound. It's also surprising quick which really caught me off guard. But is softer and warmer in the bass than the VA. I found the trade-oof between the two interesting. Normally I prefer tighter more detailed bass (VA) but there was a satisfying fullness to the PSB bass that I really liked. The PSB bass however can get unruly and out of control if placed too close to the wall. You will also need to have a larger room size and experiment with the foam plugs. Based on all the above I'd give the VA's the edge.
Both speakers are extremely musical but in different ways. The PSB's musicality comes through it's full sound that really reminds you of a live musical event. The VA's musicality comes via its intimacy and personal communication between the musician and the listener.
One thing I really liked about the PSB's is how they easily unravel large, complex pieces that may have 6, 7 or 8 instruments playing at the same time not including the vocals. Every instrument, every vocalist has its own space. Violins open up and swell as they should. French horns majestically float in the air.
Overall, I'd give the edge to the PSB...primarily because of the fuller, more dynamic sound. But the VA's are certainly more beautiful to look at and for some reason they keep their value a little bit better.
The only caveat to all of the above is that I listened to the PSB's on a Parasound 2250 amp (2 x 250 and my VA's are on a Yamaha receiver that puts out 170W. I a;ready know the effect power has on speakers...and I'm willing to bet that my VA's are going to to sound much better and bigger on a real high current amplifier. The question is will that be enough to make them sound as large scale as the PSB's? I guess I'll find out soon enough as I'm looking for an amp to audition the VA's with.