I have not heard the game an on original cart, but the Infinite NES Lives cart uses the same yamaha sound chip that is incorporated into the Sunsoft 5B mapper. Compared to the repo cart I have, the sound is very close, just a little lower volume. I only know this because I play A LOT of Gimmick! I think most people with by VERY happy with this solution. Hopefully Krikzz will incorporate this into the next Os.
As for powerpak audio, I don't have one so I can not compare. I can ask a friend to make a video though. All we need now is save states for the mapper, so I can get some practice in on the harder strats of the game.