FD2S is a 737 captain in real life, and he states the zibo mod feels more like the real plane than the PMDG model did, specifically in how the plane flies.
At the present, I think there are 7 real life 737 pilots, a 787 captain, and a few other real life pilots helping zibo with the development of the zibo mod 737-800.
I have never used the pmdg model, my understanding is that their model from the systems side is more advanced than the zibo mod, ie: more of the FMC works than currently is available in the zibo mod; zibo is slowly getting everything coded and in place, it will just take a while as he is basically the only programmer for the zibo mod, and anyone who has read the fcom for the B738 knows that the FMS is a massively complex system.
BTW, the zibo mod is completely free, that is worth a mention.
As for Xplane versus Prepare3D versus FSX, etc, etc, yup, might as well argue over Ford versus Chevy versus Dodge...