If you need size and cannot justify forking out hundreds of pounds/dollars for the speedier SSD solution - like most of us here - then it has to be HDD, no?
Although if you are asking about using the 64 GB SSD as your everyday, nippy drive, and longer-term storage is to go on a bigger, cheaper drive I don't see why that would not work.
Cue calderone to tell me I'm an arse for opening my so-called proverbial mouth.