A better speaker will sound better. Your best value and sound will be going to parts express (or similar) and buying your own. There's some work involved and you will have to make sure you have the right impedance and clearance so you are buying value getting a kit. I'm picky, so I roll my own. If you don't have time or want to mess around, buy the kit.
Edit: I just realized you were talking about pinsound vs pinball pro. My bad.