I use the Platinum and have tried on the Gold, and I can throw better in the Platinum. I like throwing, because it keeps the game moving, and it keeps my arm from becoming petrified. The Gold was a little more restrictive on the shoulder movements.
But that's just me.
From what I can tell, they're the two best. But if the throat pad bugs you and you can move okay in the Gold, go with the Gold.
If you like the Platinum:
Wilson Platinum Umpire Chest Protector - eBay (item 300284227725 end time Jan-08-09 12:20:52 PST)