Extending carts was already done to VCS (Atari's Sara, CBS RAM), so Megadrive could have done that if needed.....hold on Sega done that too (V.R. Virtua Racing).
The SNES colour difference wasn't noticeable when compared to Megadrive either. Same with the sound, there was no issue with that.
Mode 7. Megadrive beat that with speed.
The sales numbers are documented, oh well I got old mags and books too.....as I said the documented book Game Over mentioned Nintendo over exaggerated their sales figures (That book had input from NCL, Yamauchi, Miyamoto and numerous other people from Nintendo), all companies lie to make them look better.
Look around on the internet....sure, on the internet I'm a hunk with dozen girlfriends.