The PC Engine version has the clearest/highest quality sound and voice effects.
The Super Famicom version has the second highest quality of sampled sound, but it is muffled by excessive reverb. Most of the recordings were sped up to save on space and many are chopped into pieces and then cobbled together. Shouryuken for example is Shour... yu-ken. Some samples are echoed to stretch them out.
The Mega Drive version's samples are the lowest quality, but are full uncut recordings like the PC Engine version.
You can listen to the voices and sound effects by watching the video below:
The PC Engine version has the best composed music but the least realistic sounding instruments. Even by PC Engine PSG standards the sounds used are nothing special, but the soundtrack is still very well done and remains faithful to the Arcade, except probably more intense at times. At the end of each round, the music evenly fades out at the "You Win/Lose" announcement, just like the Arcade.
The Super Famicom version has a consistent assortment of typical SFC/SNES'ish sounding instruments with heavy reverb. The soundtrack has been remixed and is overall more laid-back/less heavy and less dramatic than the Arcade. At the end of each round, the music evenly fades out at the final blow. On certain stages, a crowd cheer sound effect will play at the "You Win/Lose" announcement.
The Mega Drive version has some of the nicest sounding instruments which are often similar to the Arcade. However the soundtrack is inconsistent in composition, instrument balance and often mixes in less flattering instruments that stand out against the better ones. The composition is based on the Arcade for the most part.
Some songs are slower or softer like the Super Famicom version, sometimes switching mid-song. Many tracks will begin loud and intensive before dropping out into slow and quiet. Many mix quiet hard to hear intruments against loud ones. The best way to describe the soundtrack as a whole is broken, with many tracks sounding like unfinished fan midis. This is a shame since a good composition mixed with the Mega Drive's better sounds could've been the definitive soundtrack.
At the end of each round, the music unevenly fades out at the final blow.
You can listen to the voices and sound effects by watching the videos below: