Very different games and reward systems. JP is much more linear, and you play it a handful of ways and the difficulty lies in the path you choose with some difficult shots.
GZ is more open to various orders of gameplay and the difficulty is in mastering the right order of operations to maximize score and the sheer number of objections.
The layouts are very different; GZ has more gimmicks and unique things about it, but not all of those are fun to everyone.
Personally, I wouldn't trade b/c I prefer playing JP more back to back in a home environment vs. GZ.