I'd be willing to bet that if you listened to several generations of Wilson Audio WAMMs side-by-side the sound character would be pretty much the same.

As far as pros having an advantage over DIY? I'm willing to bet a dollar to a dime that their advantage (excluding obvious charlatans like Audionote selling 2-way $28,000 speakers that they proudly declare sound like a drumhead when tapped on)is that the pros are more likely to be clear-eyed (eared?)about their results, less self-delusional because they're not working in isolation, open-loop, no feedback.