I've had the Z-2, 314-2, OB-1 and X-Shaft (along with a truckload of non-after market shafts). The first three on the same butt (unilock sp), the x-shaft on a tiger sp.
I ended up sticking with the 314-2, but I think they all played pretty well. The 314-2 just happened to fit me a little better.
I think like most other equipment choices it's up to personal preference. It's not a clear, objective "this is better than that" type of thing (like say a vette is objectively better than a lada). Some ppl like this, some ppl like that.
The best advise is to wait till you've had a chance to try someone else's... and see what you like. (or buy and resell what you don't like, but expect to lose money there)