I played the Callaways for a long time. Finally, I decided to upgrade an go with the higher priced Nikes. Unless you want spend a minimum of 450 credits, I don't think there's a better ball in the pro shop under 450 credits than the Callaway L33 ball.
For me, the Nike (L81) balls are worth it. But the effect isn't tremendous or a game changer. I would say that, on average, I probably shoot about 1.5 strokes/18 better with the Nike ball than I did with the Callaway.
It's really the slower meter speed of the Nike that I like. It makes the game more relaxing and fun for me.