The Karma uses the Triton sound engine, uses the same add-in sounds. Thus, you can add 32MB of sounds to the 32MB already built in. In addition, you can add in a 6-voice MOSS card, which adds modeling synthesis to the Karma. I thought the Karma had the same number of voices as the Triton. However, the Karma functionality replaces the dual polyphonic arpeggiators of the Triton. The Triton arpeggiator patterns can be converted to Karma patterns, giving you more control than you would have with them on a Triton.

Like an arranger, but unlike the Fantom and Motif, the Karma has chord recognition. Unlike all these keybaords, the Karma generates patterns in real time algorithmically. Arranger keyboards "tend" to be used to emulate familiar playing styles, while the Karma "tends" to sound less conventional.

None of the keyboards you mention orchestrate a whole piece for you. One way to do this is use Band In A Box to generate a chord progression and, if you do not like the way BIAB orchestrates the piece, use it to drive an arranger or the Karma.

It is hard to tell, but it sounds to me like you will want both good sounds and chord recognition. I would think a high-end arranger like the 9000Pro would be your best bet.