Ian, I agree to what you say.
In my opinion where Yamaha is winning is not just the quality of sounds in its SA/SA2 voices its the way they articulate automatically(the algorithm which Yamaha has put in) instead of button based articulations(which is also available on the Tyros 3 and above). This means that the arranger keyboardists are free to play around with their left hand chords instead of tinkering with the modulation buttons/joysticks etc. There is no doubt that the use of modulation buttons tell the keyboard to play exactly what articulation you want but the automated one if learnt will prove quite useful especially for songs with fast changing chords played by not so fast changing hands

For a synth, I can understand where the nuances become very important, there would be track by track recording and editing, so its essential to have the right articulation at the right time and also you dont have to bother about other tracks(chords) when doing the track with articulative playing.
Some of the DNC sounds on the Korg Pa3X and a majority of the supernatural sounds on the Jupiter 80 have a lot of realism in there... I heard some of Jupiter 80`s supernatural tones; they are amazing and as good as SA sounds but I doubt if there is an automatic articulation happening. The BK-7m has two of the so called supernatural tones. They, through an OS upgrade, could have added at least 30 SN tones from the Jupiter 80 to both the Bk-7m and the Bk-5...

Definitely, Yamaha has done their homework in understanding the need and application of automatic articulation through the way the keys are played. Other arranger manufacturers should come out of synth/workstation mode and lean a little towards arranger mode when it comes implementing this feature on an arranger keyboard. Quite a long post here. I`ll stop