Sega all the way, I own a Super Nintendo, Sega Megadrive and Mega CD I've played them all insanely Segas games are hidden but once I found them they ruled my world Shinobis, Shining Forces, MUSHA, Snatcher, Virtua Racing (3D graphics with smoother frame rates and more polygons than Star Fox), Streets of Rage 2, Comix Zone, Castlevania Bloodlines, Skitchin' , Splatterhouse 2, Contra hard corps
Dare I mention the Mega Drives 7.67mhz Motorola 6800 CPU actualy had a faster clock speed than the Super Nintendos 3.58mhz Ricoh 5A22 CPU resulting in some faster multi plats with smoother frame rates? (Street Fighter 2 is much faster on Mega Drive)
The Mega Drive is also 100% compatible with Master System games get yourself a nice Model 1 and Segas Master System Converter and you have a fully working Master System.
Now I will stop being a fanboy and say yes the Super Nintendo is technicaly superior in nearly every other way and both systems are amazing in there own right its just a matter of personal opinion