mbl,
I think it's just a picture illusion as both the keyboards have the exact same number of play-keys: 76. I am wondering if the actual dimensions of the keys (length & width) may be slightly different. Perhaps George could you possibly take measurements and report back?
When I auditioned both the SD1 and Yamaha 9000pro at NAMM I immediately felt at home accessing the buttons on the 9000pro (ergonomically placed in distinct color coded groupings) while I found it a little harder to discern (both find and press the correct buttons) on the SD-1 because they were all so evenly spaced (same shape/color) and situated close together throughout. Hey, the 70's look is beginning to grow on me now. Even beginning to find that 70's retro petruding floppy disk drive design pretty funky looking & reminscent of those first PC computers
Scott