I like having the option of RealAudio when I want to listen to something on a website, especially something I''m not familiar. It's a nuisance to have some lengthy download, and then find it's not what you want. Even if it is, it's good to be able to listen without the waiting.

If space wasn't an issue the best thing would be to give visitors both options. If there's not room for both, I think the streaming one is the one to keep.