Probably as you predicted as a Korg Kross 2 owner I am responding to the comparison.
The thing is they are very close and yes the Roland does have better instrument sounds, in particular Pianos, which does have a better range of sounds and tones.
The thing is the Kross 2 organ sounds on my own Kross 2 are inferior to the organ sounds that are on my Korg PA, with my PA I also have a drawbar organ with Leslie effect and this is truely awesome.
If we look at the Roland range there is not the depth of quality models with just the DS, FA, EA and BK models, and these are quite old. The top of the range FA 08 here is £1200.
With Korg there are 5 PA models, and the Krome, Kronos, Kronos LS and Kross 2 and the top of the range is the Kronos at £3000.
So it is hardly surprizing that a £600 Kross 2 is not going to have the same instrument sounds as a Kronos, conversely the cost difference between the DS and FA models is not very much but the EA is vastly inferior to the Korg PA1000 and 4X.
If you remember I agonised over which to buy, the DS and Kross 2 and I only went for the Korg primarily as it was brand new and much lighter in weight. My own hands on comparison of both keyboards in the PMT store in Manchester had the Roland sounding slightly better but for ease of creating and editing sound Combinations being better on the Kross 2.
The Kross 2 is not the only Korg where Piano sounds have been the subject of adverse comments, the PA1000 piano sounds have been commented upon in this forum by Doug and another guy posted similar on the Korg Forum.
Like any keyboard if anyone is considering either, research, watching video tutorials and then getting your own hands on trials if possible are the best way to compare and choose.