Most people will use the latest version of the game, because it will have all the bugs worked out. Some like to use older versions that had certain exploits, MK and SF series were famous for this. But in general most are just updated versions. But their are some that are different regions, some that are hacks, bootlegs and alternate dumps. To some that just want one working copy, this may be useless. But MAME's intention is archiving and preservation of arcade games. An easy way to have a nice list of games, is just use your frontend to make a favorites list. That's alot easier the trying to add each rom separately and dealing with split & merged sets.