Choose the one that sings out the most to you, and if you can afford the Platinum, then go ahead with it!
Although i would not recommend Pt for a Panerai, because it doesnt fit with Panerai's history, and a Panerai is often all about it's historical significance!
I love Platinum too, in fact most of my watches are Pt, BUT i would NEVER get a Pt panerai, for a panerai, it must be either SS ( which is historically correct) or Titanium ( which i bet my life on that if it was available back then, all Pannies would have been crafted out of this metal,but since such was not the case, a metal truly fit for a 21st century Panny) not anything else, especially not precious metals.
Hope this helps you just that small bit!
But in anycase, keep us informed of your decision, we'd all be very happy for you!
Cheers
Stephen