Since it's sample-based, it doesn't need a lot of DSP power, so it made sense to me to include both the TR-707 and TR-727 sounds to make it a bit more compelling. I left out the old LCD display with the pattern grid, as it would either be small and hard to read, or take up too much space (and in any case is probably difficult to reproduce). Instead, I included sliders for both sets of sounds, with a separate total accent control for each set. The sliders are the same size as the ones in the SH-01A, but spaced further apart (about an extra 40%) to make them nicer to use.
An extra button in the Pattern section lets you directly select instruments from the 707 and 727 sound sets, which I think makes more sense than having to toggle between modes. The extra button also makes it possible to move the "Cycle/Guide" function to the Track side where it belongs (assuming it works the same way as the Cycle/Guide feature on the TR-909, which is only available in Track mode). There's also an extra button for Menu (needed for all the Boutiques) and Trigger Out — which, just like the TR-08 and TR-09, is its own "instrument", and has a front-panel jack.