Why use MESS ?

i've just setup MAME for my arcade / classic cabinet games.

Now i would like to setup GameEx for console games.
For NES-games using the nestopia-emulator would be an option.
For SNES-games this would be ZSNES.

I've also been reading what MAME is for arcade games, MESS is for console-games. Is this true? Is using MESS to be preferred above using individual emulators? Would love to hear the advantages!

Thanks !