They are both acceptable. You hear "fifteen hundred" in the context of the 1500m athletics race. It would be normal also to say this for the year. Just for the number itself, I hear both and neither is better.

One thousand five hundred takes longer to speak but is the standard way. People who save time would say fifteen hundred because it is easier to record that number too - write 15, then 00. If you hear the standard way and record it you'll have to hear the whole sentence before writing 1500 down. There you go!