At the expense of sounding like a rah rah boy...
First...know that Dave is a degreed engineer...I believe an EE. As mentioned, the drivers that Ascend uses are custom to Ascend...meaning Dave gets what he wants from the drivers first, and then engineers the crossover. Are there more expensive drivers than what Ascend uses? Yes. Does that mean if Ascend used those drivers the speakers would sound better? No. For the drivers, Dave knows what he needs/wants, and he may not need or want what a more expensive driver offers vs other tradeoffs, cost being one.
Dave/Ascend has a direct relationship with OEMs. Most notably, SEAS and RAAL. In fact, Dave and RAAL together worked on the tweeter in the Sierra-2 to get it right, and the fruit of that labor was RAAL being able to sell a version of that tweeter to other speakers companies...this helped other ID companies. On top of that, Ascend sells more RAAL tweeters than any other speaker company...ID or not (this was true a year or two ago, I believe it still is).
Dave controls/engineers every aspect of the speaker. Not saying that is good or bad, but it is a key difference from every other ID speaker company I know. This means that he doesn't have to answer to anyone but himself...especially not marketing. He might have to answer to Dina...but I don't know.
Salk, as mentioned, builds cabinets...extremely nice ones. Drivers are off the shelf..not a bad thing, but a key difference. Crossovers are done by a third party (not the same third party for all their speakers), also not a bad thing, but also key difference.
A couple more things....Dave's testing/measurement equipment...I don't know of another ID company that has the same capabilities. Dave actually has a background in audio industry, he has worked for one of the biggest names in audio. Ascend was not built from a hobby....it was built because it was what he loves to do, and was trained/educated for it. I know there are aspects of the business that he doesn't like, but hopefully they never outweigh what he loves about it.