I am curious about the difference of sound considering the stiffness of the enclosure (the platinum's weight is higher) and the difference of the drivers for high frequencies and midtones.
I once have auditioned the Gold 200 versus the Platinum 200: the mids of the Platinum had more 'airiness' (probably because of the bigger mid driver of this speaker), I only have heard the Gold 300's but I didn't notice it then.
The Platinum's went deeper and tighter (concerning the lowest frequencies) than the Gold 200's.