You're joking, right? The mythos of "mechanical is better" has been so thoroughly debunked by professional play that to claim it is somehow a "better tool" requires deliberate and willful ignorance.
A pro is paid to use a product, that proves nothing except that the person was paid to use a product and not one thing you said actually debunks what I said.
Look at Nascar, just because a driver drives a Ford, it doesn't mean anything about how he actually feels about Ford, the car doesn't even relate to a car on the street. However, if he wins, you can bet he will say the Ford was the best... Because he is paid to.
Truth is, if you want to see what parts actually work better, look one notch below those being paid. They
tend to run what they believe to be the best. Unfortunately, even they can get caught up in hype, but generally they will run what they believe to be the better product, even sponsored will sometimes swap out and just add sponsor stickers. I have seen it in cycling where one product is so good, most of the sponsored riders ride that one product, and just put a sponsor sticker on it so it looks like they are running the proper part. A good eye can spot the difference though.
Honestly, pros are the last people you should be looking at towards what products are best. As I said,
a good carpenter can make bad tools look good. Which is exactly what a sponsor wants. In this case a good player can make a bad part look good. To the sponsor, it doesn't even matter if that part needs to be replaced regularly.
So, why is mechanical actually better?
Domes can be less consistent, especially over time. Mechanicals can be tuned, Jailhouse Blues are a PERFECT example of this, as are o-rings, adding a plate, even changing the key cap type. Not all of these necessarily make one item better than another, some do nothing but add comfort, however sometimes even that is important.
The British Cycling team last Olympics (and the regular race season) went so far as to lug the rider's mattresses from one hotel to the next, as well hire as a team chef, and brought their own drinks. This way, they always felt at home between races and limit outside influence. Was it a significant amount of performance gain? No, even they admit it was minimal, however, a teeny bit here, and a teensy bit there adds up enough to where non performance enhancing drug riders were keeping up with those who were (and yes, riders knew which riders, including Lance were doing it, it wasn't even hidden). These little edge on the competition is what all sports are about, getting that teeny little fraction of a bit of an advantage, because sometimes, that is what determines the winner from the loser. Keep in mind though, sponsors sometimes interrupt that in the name of profit.