Hoo boy. That is a tough one, as I really do love both. I have to say that I LOVE LOVE LOVE PUB, but I love PLB less, only because it primiarly uses the barbell, and it gets REALLY old swapping the weight plates on/off. On the other hand, it's effective, no doubt about that.
And the Gym Styles? Well, they just rock. Seriously, they are all tremendous.
Do you know whether you prefer a 2 day or a 3 day split? With PUB, you cover all the UB in one workout, where the GS split UB over 2 days.
While I don't think I can give you a recommendation to go one way or the other (I do love them both, and use them both often), the good news is that you seriously can't go wrong, no matter what you choose! I know that's a lame answer, but it really is true.
m.