I've got both synths, the 5 and the 6. I use them both daily and love them each for what they are. No question for me that the 5 has a more immediate and weighty sound. Gravitas is a word that works. It's very possible to match certain patches between the two synths, but on a gut level, there's still a difference. That said, they're both mighty synths. The Prophet 5 simply has a Sound, while the 6 is is more versatile in its range of sounds, if that makes sense.