I prefer the original shaft by the cuemaker,  which is one of the main reasons why I chose that cue in that cue in the first place.
Shaft taper is a big deal and I like certain tapers like Ernie Martinez,  James White, Joss West,  Tim Scruggs,  many more even Schon.
Most of the aftermarket shafts I have play real good like Predator 314 & Z,  Tiger-X,  and my original Universal Smart Shaft is excellent.
I sold a Z2 to a friend who loves it, great looking shaft,  I never played with it but I like the way my Z shafts hit for some reason.
I've picked up a lot of stray shafts in cue deals so I get to try a lot of stuff.
You're probably on the right track with the Z2 from some of the feedback I get,  there has only been a couple of these LD shafts that I did not like.
The Predator shafts seem pretty good to me.