Everyone has their own preferences; If you're skilled enough to play every note in the chord (no shortcuts) you've got nothing to worry about. The last time I tested a Ketron I was frustrated because instead of recognizing Minor 7ths in all inversions, The SD3 more often interpreted it as a sixth chord.

I've tried just about all of the brands and I find Roland allows a wide variety of common chords with the fewest notes pressed, and the least amount of hand movement. With Bass Inversion activated, Rolands will also recognize many slash chords with only two keys pressed. For chords like C/G, Korg requires you to also play the third above.

Amazingly, recent Casio models (those introduced in the last few years) seem to have an IMPROVED version of Roland's Chord Intelligence. Unlike Roland, they recognize "power chords" when you play 1+5 (i.e., they drop the third from the accompaniment pattern.) There is also a user setting to suppress recognition of the 6th chord, to avoid the tie-up i mentioned with Minor 7th. Very thoughtful and logical, it's a shame that the keybed itself is so flimsy!