Without making this a long and drawn out explanation, I would highly recommend that you try both shafts and make a decision on your own findings.
I personally can play with either, however I prefer the Z2 because it fit's my game style much better.
APA Senior Division League Rep.
APA S/L: 8 Ball 6, 9 Ball 6
Playing Cue: Predator Special Edition SE-3
Playing Shaft: Predator Z-2 w/ Kamui Clear Med
Back Up Shaft: Predator Z-2 w/ Kamui Clear Med
Break Cue: Predator BK2
Jump Cue: Predator Air
Case: Predator Sport 2x4