most (all?) of these keyboards give the thumbs more to do than merely pressing the "space" key. This is awesome, because thumbs are strong and relatively quick.
However: with the exception of those sculpted keyboards (Dactyl-ManuForm et.al.), the thumb keys are triggered by lateral thumb movement, which can be troublesome.
I had absolutely no problems using traditional keyboards for ~30 years, but decided to proactively switch to a split keyboard (ReDox) nonetheless.
Mostly it's great, but I developed pain in my thumbs from the constant uncommon (to me) lateral thumb movement.
I replaced the thumb switches with lighter ones and remapped my keyboard layout to use only 4 of the available 12 thumb keys, but it's still not ideal.
I'm thinking about building one of those sculpted keyboards now.