Interesting question !!
With my DA200 concerto or Elkavox 83 midi accordions i have the following set ups (far too many )
Technics smac1200 ,kn7000 , gem XP expander and Tyros 2 .

they are all good !
but i have to say for me I like the Technics brand best of all mainly for one reason :- The Gem and Yamaha are very poor in song specific styles !! ie glenn miller genre with all the correct intros/endings

It's not only the miller styles it's song specific style complete across the spectrum .

If you folks know where all the song specific styles are for Yamaha and Gem please let me know !!!as I've had not real luck searching for them !!!

Technics did such a good job with the styles library via technote in the Uk .
I'm sorry to say trying to convert successfully to the other two brand leaves a lot to be desired !! not good enough to gig !!

Regards .............Giovanni