RE: Turtles, You can't trust youtube for sound quality. That SNES example is clipping, and the Mega Drive one is emulated (SNES maybe too, hard to tell in that mess).
I just popped them both on to compare in real life in pretty much ideal circumstances, (VA1 AV Terminal Mega Drive, Super Famicom Jr, to Pioneer amp with quality floor speakers).
Music is marginally clearer in the MD game, but it's overall a worse audio presentation, due to the overall mix including sound effects.
The SNES game uses the bass-space for sound effects, so hits on enemies (and the wrecking balls dropping in stage 1) are huge and meaty sounding. On MD the hits are wiffy little crunch sounds, that sit in the same space as the drums and get lost. And of course the speech samples sound like turd on MD, but are quite good on the SNES.
Overall the SNES game just sounds much fuller. Larger sprites on the MD though, and lower colour suits the game, looks more arcadey.
It's only one game, it doesn't prove anything, except that youtube audio doesn't prove anything
This has been done a million times, they're very different sound chips, and while it's a fact the SNES sound chip is vastly more advanced and flexible, in the end it's game by game because music is art.
As a Konami fanatic, I'd listened to the SNES one hundreds of times for at least three years when the first Konami MD games showed up. And to me it sounded like a lo-fi clone, which it is, it's a 'port' of a jingle that was developed on the SNES first.
Trivia: SNES version has a pink line, PCE version a blue line, MD a green line. SNES version was the 'real' one, as it was used as an animated logo made of an LED array on top of the Konami building in Tokyo in the 90s.