I consider music of 50es and 60es (XX or XIX centuries like cha-cha-cha and polka as evergreens. If you want play this old dance music, than you need old arranger (like G-70 that I own since 13 of January 2005).

But even be-bop and hard rock you can play Karma as well as auto arranger (with 8 style variation), slightly different in flavor. I think that you can program cha-cha-cha and polka in Karma too, but there are no factory preset ("combi") for them. Because when you get Karma, you immediately forget all cha-cha-cha and start to invent completely new music

Contemporary music with many layers of fast synth and slowly moving pads you can't play with arrangers but can play with Karma (e.g. in Korg M3) with same "8 style variations" as in ordinary arranger and chords+solo split in keyboard.