Most of the korg arranger buyers (until recently ) are mid east or east EU players or most of their set is Smf playback or used in studio/live with the band using korg's superior edit functions.

On the other hand , if you play more 4/4 music , more western pop,rock,simplicity and non generic nature of simple styles (8/16/ballades , not rap or funk), yammy will make it easier.

Once you start using Styles as a major part of your gig, people start to have frustration with lack of styles (korg/Roland) compared to Yamaha .not to mention horror stories about trying conversions and bad results.

Yamaha - hardware not so good,look/ more styles out there/ better solo voices (SA to DNC), drums -weak but workable if you are a singer ,,simpler to use,easier to sound good/ make you sound good right now !(not after editing/manipulations)/more generic styles that fits MANY SONGS (compared to Korg -more song specific and hard to use the same style in other song- you'll notice after you bought the KB and start working,since styles are not as easy to get as Yammy,too late for you to return)
.other thing that I forgot to mention is SMF style mix in Yamaha (load a crappy drummed Smf,replace the drum track with arranger thrum track-your ROCK Smf will have reggae beat in no time).
Korg- relatively better hardware and looking(IMO ), better editing, overall punchier sound,better sequencer, not as good RH sounds compared to some SA ,relatively last longer ( no wheel/pot/jack problems after 2-3 years)



Again we are talking IN GENERAL.Korg has better file system,songbook,drums/bass,VH,hardware and But Yamaha is easier flow /better 3rd party support and better solo voices.

Korg us the way to go if you want A kb to sequence,studio,live playback or with a band,with moderate arranger work.

Yamaha if your gig is more arranger (western music) oriented.