MVS or Multi-Video System cart boards and physically bigger than Advanced Entertainment System carts. The Roms or Chips set that are on both boards are the excat same programs. It only reacts different depending on what 'Type' of board you plug the game into. This of course makes home conversions cake seeing as SNK only has to slap some Roms on AES boards, Makes a Box, Insert, Manual and you have a hoem game. You'll find out overall that many MVS games that are currently out can be played on a Home system with a Convertor. The later titles tho require a convertor like !Arcade! that will allow the convertor to play encypted Roms.
SNK started doing this recently around KoF 99 to prevent hackers and such t dump the roms on the net or burn them to eproms to make a profit on 'Unofficial' SNK MVS carts. Several memebers here have gotten those carts and tho the games work the quality of the work is either very good or shit compared to which bootlegger did it.
I kinda went into a rant there but I hoep this answers your question a bit more clearly...