A six-voice limitation means that basically you're left with playing triads with single or double basses, and with patches that have short release times. That's still allows for a lot of music to be made. But, for example, if you tend to
play your arpeggios with your left hand using a patch with a long sustained piano-type release time (
https://www.youtube.com/watch?v=D6vGjl3Y18A), then you find yourself running out of the six voices very quickly, especially if you want the notes of one chord running into the notes of the next chord. Then the manner in which you play the arpeggios suffers, in that you keep the choice of notes to a minimum - say, eliminating seconds, sixths, and sevenths. It makes for a strong practical argument in favor of eight voices or more. For such playing, the Prophet 12 looks very attractive. Except for the price, I could see using the P12 just as a left-hand instrument.
I realize my preferences in these matters are generally not shared by others, but they are the reasons I'm always looking for the keyboard player's synthesizer. For me, the most important part of a synthesizer is the keyboard; if that's not right - including the number of notes that can be simultaneously triggered - then all the rest is irrelevant. This is why I'd be happy with a synthesizer that had no arpeggiator, no sequencer, no effects, nor a host of other features that I'd be willing to sacrifice, if only to maintain the fundamentals of synthesis together with high keyboard and voice count standards. Again, I realize these are unpopular views among synthesists, but such happen to be my very real needs, so I put in a word for them.