Native instead of stretched pixels or black sidebars. Silky smooth, locked 60 frames-per-second performance.
However, Sega never greenlit the official project. While Sega never released an official statement detailing why, two major roadblocks are widely recognized: 1. The Music Licensing Nightmare
The original Sonic 3 has a fractured soundtrack. The PC and later re-releases replaced several iconic tracks due to licensing issues. Sonic 3 RSDK allows you to choose. You can play with the original Genesis/Mega Drive music (the Jackson/Brad Buxer tracks), the "PC" replacement tracks, or even fan-arranged orchestrals. For many, this was the first time playing Carnival Night Zone with the correct, funky bassline on a modern PC.