When buying a cue, you should really go try them in person (maybe find people in your hall who have the same cues you are interested in and ask to test them out). If you don't have a local dealer, the Predator SP line are pretty hot selling cues, so I imagine you will come across people who have them. Also, some of the online vendors have pretty good return policies if you don't mind the hassle of shipping stuff back and forth in the case of a return.
That being said, assuming you can't test the cues out... For the joint, that is such a personal preference, you can't go wrong with wood or steel. If you already like the steel joint, you like the stiff hit, and that is what you are used to, stick with it on the Pred. If you prefer a softer/slower hit, the wood joint is fantastic and it really lets you feel what's going on, but if you aren't used to it then it will just feel weird until you get used to it.
For the shaft, a lot of players that I know who bought the Z ended-up going back to the 314. The thinner Z pivots around on your bridge more easily and if you don't have a clean stroke can easily hit the cue slightly off, which makes it hard to handle for most people. If you have a clean stroke, you may not notice this and may enjoy that you can hit higher and lower on the cue ball with the smaller tip.
If you're worried about the Z being too small, you can of course have a 314 turned down a bit make it thinner, and yet still a reasonable size. Or, if you just want a little more action, you can shape a 314 with a dime tip (if you are using nickel). There are a few ways to ride that horse.
If you just want to know what others have done, I spec'd a 4-point, 314, wood/wood, with no wrap for my friend (she already played with a Lucasi SP which is also wood/wood with no wrap). When she got it, I played around with it for a bit to see if it played as I expected... And it did not disappoint; that cue was sex on a stick.