I posted to reemphasize Dave's point-- if you're used to the "easy" mode on a Roland, Korg, GEM, etc., the SD7 is a much better choice than the SX900.

If I could play all the component notes of a chord timely and accurately, I wouldn't bother with an arranger- I would just get an organ or synth/workstation. Easy chords are gold!! On a Roland for example, you can actually play DOZENS of chord types, including many slash chords and tensions, with one, two, or three fingers. Yamaha isn't an option unless you're prepared to relearn everything. Yamaha could fix this by changing their menu structure for chord recognition and adding some options. But Yamaha knows everything. Yamaha is always right! I doubt they ever will.

Ketron arrangers are rare unicorns, so I haven't had much seat time with them. None at all with the latest generation of products. What I recall from the SD5 is that for the 3-note inversions I use to trigger minor 7ths on Roland and Korg, Ketron tends to recognize these as a 6th chord. This presents a problem for me, because i would have to re-learn my hand positions on songs I've been playing for years.

Now I don't know nearly enough about music theory to argue that minor 7th chords are more "important" than 6th chords. What I can say is that minor 7th chords appear much more frequently in the pop music I like to play. I have a lot of Hal Leonard-style EZ-play books, and 6th chords almost never appear in these. Even the full SATB sheet music I've purchased seems to have more minor 7ths than 6ths.

[Getting a bit off-topic, but recent Casio products have a mode that actually EXCLUDES recognition of the 6th chord, making minor 7ths playable in all inversions. Casio's simplified chord fingering logic is actually very good. Unfortunately their keybeds, MIDI implementation, and overall quality is NOT good! However, the existence of this mode shows that Casio's product designers also favor minor 7ths over 6ths.]

If Ketron has fixed my "problem" with their recognition of minor 7ths, I might start saving up for an SD40. Unfortunately there's no way of knowing. Too many combinations to ask you to try, I would have to test one for myself. Way too expensive to just "take a chance." And if there are problems, it wouldn't be easy to trade in or get my money back. So I stay on the fence. Good thread though!