Uncharted is like 3gb, JSR is 1.1gb. Not sure about Gravity Rush but someone will tell you.In most cases I'd go physical over download, but currently I have Uncharted, Gravity Rush and Jet Set Radio from PS+ that I'd be transferring over. Add to that any other games that get added to PS+ and some PS1/PSP/PSN games that I could also potentially transfer over, but probably not too many at once.
I guess 16GB might suit me better for the time being.
Honestly I might just go for the 16gb and save up or wait for a sale on the 32. Considering most PS1 and PSP games aren't larger than a gig, you should have a decent selection. Worst case scenario is that you end up selling the 16gb or you keep it as a nice spare or alternative region account.
I don't think you can really go wrong either way.