For a home-use only Donkey Kong it's pretty easy to get an original Nintendo button (or a good repro
https://www.mikesarcade.com/cgi-bin/store.pl?sku=TKGU-23-32), and a new microswitch (
https://www.mikesarcade.com/cgi-bin/store.pl?sku=TKG-23-10). This whole setup would cost about $11 from Mike's Arcade, and last forever if you're the only person using it--since it's not getting cigarette burns or getting kid snot on it, like in an arcade. And if you're the type of person to layout the cash for an original cab, an extra $11 investment seems negligible.
So there's no real argument that the original hardware experience is unattainable to those who own their own dedicated cabinet.
Then why use a newer button?
If top players favor these newer buttons, the only logical conclusion I can come to is that: they feel these new buttons are advantageous. The advantages are up for debate: reliability (works every time like the first time), less maintenance (the original setup is a pain to keep accurate over time), shorter throw (no having to account for lag), etc. But I think that top players have examined button options, and have made their choice based on their knowledge and experience. (I mean, I spent hours on the first day of the Kong Off 6 just getting my CP up and running properly, mostly due to the shitty button situation, and my original CP having an 8-way joystick. It sucks. I get it.)
Obviously:
--it makes a difference
--it's not something people could have used in the early 80s
--and I don't really give a shit if you use one
When I first started playing, I really thought people were losing their minds over the whole 8-way joystick thing, and I didn't get it. I understood that my status as a neophyte was why I didn't fully understand the intricacies of different Donkey Kong control mechanisms, and I decided to sit back, listen, learn, and develop an opinion based on knowledge and experience--instead of spouting off and looking like an asshole. The internet seems to be full of people who haven't learned this lesson.
The newer buttons are better (for some), that's clear. Does it matter? Yes. How much? Not enough.
4-way joystick matters. Buttons can be a pain in the ass, use whatever works for you.