I myself have been pondering since last week too!
I'm thinking of going for the 1TB, eventually moving to a bigger hdd because with all the film & photography work I do, I'll fill it up in no time.
With the prices of SSDs expected to tumble pretty damn soon... I'm thinking of running a thunderbolt SSD.
Give it a couple months on SATA and see if you really do need the SSD... Not sure as to how installing OS on a thunderbolted SSD would go but as far as I know the biggest gain is in boot time which is pretty pathetic.