This is one of those questions I've always wanted to know the answer to: What is up with the nine minute snooze on alarm clocks? Our friends at Switched thankfully found the answer to this brain-teasing question for us.
Basically when the snooze feature was added to alarm clocks in the fifties, the new parts needed to mesh with existing gear configuration. This forced engineers to create a snooze that lasted just over nine and ten minutes. Apparently ten minutes was too long for a snooze because people were falling back into deep sleep, so nine minutes became the standard snooze time on alarm clocks. It's a standard we still use today.
I don't know about you, but a two or thirty minute snooze usually feels the exact same to me! I'd say the best alarm clock/snooze button is training your body to wake-up at the same time everyday. That way when your alarm clock goes off, your body doesn't go into shock and a few extra minutes of snooze time doesn't completely throw you off. It's not a science, but it seems to work.