Very different kind of sound.... i'll try to hit everything in bullet point form as I can be a bit wordy from time to time
-VSA uses rear firing ambience tweeter that is adjustable to create more depth, more 3D type image and soundstage, as well as improve ambience...
-VSA crossover and design creates imaging and soundstaging capabilities that exist from way outside the sweetspot. Go way off axis, stand up, move around the room, etc. The VSA is pretty much the same tonally and still maintains image even way off axis. Speakers are still disappearing from waay off to the sides. The Ushers can't accomplish the same thing.
-VSA goes for more balanced sound top to bottom. Usher has more punch and drive to things and emphasizes the midbass a bit more. Usher loads the room more with their dual 11 inch woofers and gives the impression of more impact and deeper bass. But VSA in fact actually has lower frequency performance. It's just not the same impact. VSA goes for more bass detail and pitch definition. Usher wants to rock you upside the head a bit more and party.
-VSA is a bit more neutral from top to bottom whereas Usher has its own character. Usher midrange and tweeter is a bit more ruthless than VSA, but VSA is far from a slouch at all in resolution, detail and transparency aspect.
-both like power if you give it to them, but can work with much lower power if it is good stuff. Lamm with VSA is a very nice combo...
-VSA is a bit more "traditional box" looking in spite of separate mid/tweeter and woofer box design than the curvy Be-20. Be-20 takes up more real estate as well because of pitched baffle. Last significant other MUCH prefered Usher. Current significant other much prefers look of VSA. personal preference I guess....
-a lot of it boils down to price. VSA is reference class, but MSRP is now $28K. Usher Be-20, even with price increase is only $18.8K. $9K price differential is nothing to sneeze at. I chose Usher because I liked the lower price point, especially before the price increases. I felt I could sell more of them as values than the then $25K price of the VSA VR-5SE.
I've only heard the VR-5 Anniversaries once in show conditions and I didn't like the electronics used in front of it. I've heard the VR-5SE a number of times and had the 4SR on display for 1.5 years. My customer had his Anniversaries custom wired with JPS Labs and he's ecstatic with the improvement over the existing VR-5SE. I haven't heard his pair yet as he's not just down the street from me. I will say that the VR-5SE is the only design with the Scanspeak dual ring tweeter that I've really liked. I've heard the VR-9 a number of times and spent quite a bit of time with a pair of VR-11s. The 5s have a lot of the amazing traits of those bigger speakers...