all white keys is easy to play a scale without thinking, but I find it much harder to play well than keys that have some sharps or flats. that pattern of 2-space-3-space on the black key shelps to anchor your hands. I'd take e-flat major--its far easier to play than c-major.
Transposing is harder, but the vast majority of piano litature is never played tranposed--you play the notes on the sheet music. I've tried some of those new layout keyboards like the Linnstrument, and I'd never try to play a Beethoven sonata on one.
To be fair, perhaps most sonatas include transposition within them, only it's written out.
This actually presents a hurdle for me, because if I learned a theme in G, and now I have to play it in D I feel like I know it, so I don't practice it as much as I did initially and it ends up in this weird limbo where I know what I'm supposed to play, but haven't properly trained my fingers.
But there's plenty of stories of Liszt or Chopin transposing music on the spot. Jazz too.
Transposing is harder, but the vast majority of piano litature is never played tranposed--you play the notes on the sheet music. I've tried some of those new layout keyboards like the Linnstrument, and I'd never try to play a Beethoven sonata on one.