I always compare with auto brightness off
But this photo demonstrates it plenty! Awesome!
Looks like your 9.7 may have been a bit sub par though acceptable, but that 10.5 indeed looks nice!
Maybe I'm just traumatized from three units with yellow edge at bottom, but the bottom looks ever so slightly darker which i could totally cope with vs the yellow strip (which i dont see on yours!)
Did you ask to purchase a demo unit?just kidding
To be honest, with my experience of the display lottery, my 10.5 is pretty much as good as I'd expect tone-wise, and from a panel with backlights firing from one edge only.
It's always a problem inspecting a screen in an Apple store, with their perfect lighting.... and I do believe they cherry-pick the best units for display