The comparison between Wilson and Vandersteen speaker designs is an interesting one. Richard has designed and now makes some of his own unique, groundbreaking drivers (using balsa wood, a brilliant idea imo), and uses all 1st-order x/o slopes---he is a proponent of phase-coherency in speakers (whether 1st-order filters remain phase-coherent away from the x/o frequencies is an issue of some debate). Dave has drivers made to his specs---making changes to OEM models, and his drivers are, as tomic601 mentions above, wired in opposing polarity (as they are in many other, if not most, speakers). Each also has his own idea of the best way to deal with enclosure issues. (As a long-time fan of planars, I find it amusing the amount of effort is takes to get dynamic speakers to do what planars do inherently. Of course, planars are not without their inherent shortcomings.)
For years, Vandersteen offered only the Models 1, 2, and 3, priced well below Wilson’s products. There were some dealers selling both brands, Vandersteen’s to those of, shall we say, more modest means, Wilsons to the more affluent. But there were (and are) people who can afford Wilsons, but prefer Vandersteens.
With the introduction Model 5, Vandersteen was now in direct competition with Wilson in price. The two men’s designs sound very different; some find Vandersteens slightly warm, soft, and veiled, others Wilsons too bright and analytical. But a dealer selling both faces a dilemma---which does he "push". I know, I know, a product should sell itself; let the customer hear both, and decide for himself. But here’s a little secret (already known to some here): the more product of a company a dealer sells, the more of a "preferred" dealer is he by that company. If a dealer sells $500,000 of Wilsons and $500,000 of Vandersteens a year, he is less valued by each company that he would be if he sold $1,000,000 of either of them.
I had (R.I.P.) a well-known dealer friend who sold both, but told Richard he didn’t want to stock, audition, and sell the upper-priced Vandersteens, only the Models 1, 2, and 3. (The reason being he wanted to reserve the higher-priced range for Wilsons). Richard wouldn’t agree to that (I wouldn’t either), and the dealer and Vandersteen parted ways. I thought the dealer was making a huge mistake, but it was his store, and he was a very strong-headed and opinionated guy. He did sell two planars---Quads for ESL enthusiasts, Eminent Technology as his magnetic-planar choice. It was he who hipped me to the superiority of the ET push-pull driver over the single-ended Magnepan.