PAM 306Ti or 316 Plt
Really hard to let others make the choice for you Chris!
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
Not even close....I would vote 100% to the...
316 !!!
I have seen both in person and the Platinum is the most "substantial" watch to date for Panerai. I love the 48mm size and the watch is just plain impressive!
Trust me..no comparison!
Get the PAM306 since you prefer the Luminor case over the Radiomir case
The PAM306 tourbillon is in titanium and comes with a brown dial, so it's a pretty nice combo. If you want to get a precious metal Luminor Tourbillon, maybe a white gold version will come out next year? Don't think a platinum Luminor tourbillon will come out since there haven't been any platinum Luminors yet.
Cheers,
Anthony
My thoughts
As you have already indicated your preference on luminor case and given the price advantage, it's easy to lean toward the 306. Having said that, I would like to state a few counter-points:
-When you're getting into complication like in house tourbillon, I'm not so sure whether historical significance will play such an important role so YOUR preference on the material of choice should play a bigger role
-USD$15k is obviously not small change, especially in the current economical climate. Having said that, it's abt. 15% of the difference in list price. So value for money, I'm not entirely convinced that the 306 is a better buy in a monetary sense
-As Craig pointed out, the heft of a platinum piece is really nice. Have you tried them both?
As Stephen pointed out, buy what pumps up your heart beats and gets your adrenaline running high. Who cares what we say over here? 
All very valid points, thanks for the input..
..appreciate it, and indeed it has helped me make my mind up, going for the 306. A few reasons why, firstly the watch will be a daily wearer for me, and as I have worn a 1950 8day Luminor for the past few years, I have been impressed with the robustness of the watch. I am a big chap at 6'5" and wear a 44mm watch comfortably,47mm is just about ok, I have a feeling that as a daily wearer the 48mm might be a little big.
I also am indeed smitten with the brown dial, as I have not had one before, so that will be a nice refresh from the black. Also I do have a Radiomir 197 in gold, so if I feel like a radiomir day then I can still have one! And last but by no means least, saving of $15k helps too
Sorted!...hmmm but then again i do like Platinum!... No 306 it is, will post up some pics when it arrives, cheers
Great!
Looking forward to your thoughts on the the PAM306 Tourbillon when it arrives. Please do keep us updated!
Cheers,
Anthony