Hi Ed,
In my experience, the primary difference between the Pt and Wg version is the lume applied to the hands, with the Pt version having no lume and the Wg version having it.
Aside from that, I have noticed subtle differences in the hue of the dial on each, similar to comparing the Lange 1 stealth and night owl (each Pt and WG respectively).
There also exists a LE of the timezone which is WG and has blued hands, called the Buenos Aires edition. I do recommend you seek out this version as the blued hands are fantastic.
I may be missing some other difference, but those were the first things that popped into my mind. Both versions come with a tang buckle.
Best of luck in your decision!
Colton