Sram uses a battery, and is faster and has virtually unlimited write-rewrite cycles.
Flash ram is not dependent on a battery, and is a bit like a disk in function. It is slower, consumes power from your Zoomer during read-write times, and does have a write-rewrite limit. However, that number is quite high, so by the time you are wearing out a flashram card, you'll have something else anyway. (There are wear leveling programs for some flash cards -- I have one for my HP card).
Happy New Year!
Craig