Gotta be 10 voice for me. 6 voice is my absolute minimum, it's just how I work. And no, for recording you can work with 4 voice etc, and don't always 'need' bass notes with the left hand, understood.. esp if you've got a real bass guitar doing that
.. however just as an instrument to enjoy without feeling too limited the Prophet 10 is awesome. All that Prophet 5 goodness but in a 10 voice! I currently have a Prologue 16 and love having that much polyphony in a VCO analog synth. The Prophet 10 comes close with 10 voices and is one of very very few genuine VCO polys that have more than 8 voices. So it's in a different league now.
Also if we think about it, being a 'restricted on features' re-issue/revision that hasn't gone crazy, the genuine power update to the rev 4 is the double polyphony. Like the P10 in the 80s tried to do but failed due to heat issues and then due to being a cumbersome double manual beast that wasn't exactly sexy/desirable.
Prophet 10 Rev 4 - 2020 is to me the ultimate Prophet. 5 Voices was also offputting to me for many years regardless of what old bands managed to coax from those limits. 10 Voice is a nice amount (like my old AN1x which was a VA based on the Prophet 5) I always found 10 perfectly manageable and more than enough when you wanted longer releases without note stealing.