It's a tough call. I think Omega Boost is better paced and is a more technically impressive game, but I personally prefer the PD universe. Of course, I like Space Harrier better than any modern rail shooter, so what do I know?

I'm almost certain that I read somewhere that Omega Boost was developed by many of the same people as PD, after they left Sega. If I still had them both I'd check the credits, but I got rid of my saturn and PSX stuff ages ago.