I recall the Egg Dragoon just as an ass as it was in '06. Hooo boy, not looking foward to that rematch.
Dragoon's from Unleashed, though.
Also, the PC version can load levels faster and run things smoother if you have a high-end computer, but otherwise its only 'advantage' aside from resolution is the possibility of Sonic Retro or some other site hacking it sooner or later. Hell, someone might mod Classic to 'perfection', but I won't hold my breath. So there's no reason to beat any boss on Hard aside from self-gratification or if you're trying to S-rank everything.
Also, since the Casino Night pinball DLC (no actual stage, the 3DS version gets a full stage) is part of the game data, some people have had it work randomly on the PC version and modders will probably unlock it sooner or later.