The Mega Drive version has a dark blue shadow for most of its text that is hard to make out against a black background.
The PC Engine's KO bar permanently takes up a horizontal strip across the screen, so there are unlit peace sign icons before a round is won. However, the KO and icons are detailed and shaded. The Mega Drive version has a secondary color for minimal shading and the Super Famicom is unshaded.
The PC Engine version is the only port that has the different colored clouds like the Arcade.
The Super Famicom port has a unique "O" shaped star that doesn't pop like the other versions. It does however have a yellow colored star like the Arcade. The frame in the PC Engine and Mega Drive ports that pops is actually the same as the Arcade's, only instead of squishing it to match the console resolution it was turned on its side.
The PC Engine and Mega Drive ports retain the blood animation from the Arcade, while the Super Famicom version just recolors the sweat pixels.
The Super Famicom and PC Engine versions have similar Hadouken and Yoga Fire sprites. The Mega Drive Hadouken loses a little color, but the Yoga Fire has little shading left. The Tiger Shot is missing pixels and uses dark colors on the Super Famicom version. The Sonic Boom color and shading is the same on PC Engine and Super Famicom, but the PC Engine version uses horizontal opposites instead of diagonal opposites for frames.
Both the PC Engine and Super Famicom versions have two colors of vommit like the Arcade.
All three versions have the same amount of shading and only differ in tint and vibrancy.