Long ago, I switched for ergonomics reasons. My fingers were aching from using hard Dell rubber domes at work (and stupid scroll-wheel...), and the MX Brown were much lighter and gentle to my fingers. I used MX Blue with O-rings at home, which was even better but I could not use it at work because noise is an issue. The blues are light and with two kinds of feedback. (that some think that the bump is too small is a subjective thing)
Some scissor switches are light and feel nice, but it is rare to find a
contoured keyboard with them (I think I have only ever seen
one, and I missed to jot down the brand, sorry). The industry trend for scissor switches has gone in the wrong direction though, with flat chiclet keys, lower key travel and wider keys: being detrimental to key feel and accuracy.
There are supposedly studies that say that bottoming out hard always would be bad for your fingers. I think that also includes bottoming out on scissor switches.
After testing various switches, I settled with Cherry MX Clear. Other people find this too hard, but to
me I would describe feeling like "a scissor switch on top of a spring" because after the tactile bump, the switch actuates and the spring is then hard, cushioning my fingers. This makes my key stroke shorter on these shorter than on any other switch in the MX family, but I do admit that it took my a while to adapt to this typing style. (It is the
area under the force-displacement graph that counts for fatigue, not just the force or the displacement).
I don't see much value in switches with linear feel, though, from an ergonomic standpoint. Some people love them, but that is purely subjective.
Another benefit of mechanical keyboards, with Cherry MX switches is the supposed long
total life. I know kids these days buy and trash expensive gaming keyboards like crazy, but real men get good tools and
maintain their tools.
Nowadays, good keyboards with Cherry MX (or clones) don't actually have to be that expensive: there are lots of brands that compete, with various clone switches. You could get a tenkeyless that feels and performs great for years, with doubleshot-moulded keycaps for much less than a stupid low-profile keyboard from Apple or Microsoft. Just do your research and compare beforehand.
A keyboard with Cherry MX switches could be repaired, by replacing the switch or keycap. Other keyboards on the market are so flimsy, made from tin foil and glue basically, that the only option would be to throw them away.
Also, with mechanical keyboards switches and keycaps being somewhat standardised, you could upgrade and customise them. (Just don't get sucked into collecting expensive different-coloured custom key sets or "artisans"...)
To summarise:
• Contoured/Sculptured keys with a dimple in the keycap (
cylindrical is norm) is objectively best for typing accuracy, ruling out most low-profile keyboards.
• You can get one that is light (to actuation) which is objectively better for your fingers. (But you could also go wrong here)
• Repairability. High quality is attainable.
Unfortunately, mechanical keyboards will need some customisation to not be very loud.
There have recently been some lower-profile mechanical keyboards, even clicky with contoured cylindrical keys, but I still don't think any is really great. Clicky or linear, and loud is the norm for mechanical, not silent and tactile.