This from another recent lunch conversation –
1. Story points are a pure measure of size and complexity>
2. Story points are relative (say, with respect to the simplest story) and so have a much longer shelf-life
3. Story points are usually independent of who gives the estimate (as in, an experienced developer and an apprentice can usually agree on something like complexity fairly quickly)
4. Story points avoid the need for discussions like “what are *ideal* hours, really?” or “My ideal hours are different from your ideal hours, stupid.” These add no value.
5. Story points don’t influence behavior (e.g. Parkinson’s Law)
6. Story points are easier to work with – especially when product owners start to wonder why “3 ideal days take a week…”
7. Story points are more fun – especially when they’re in units like gummy-bears, polar bears, or other endangered species.
On a slightly different note –
When you use a geometric series for your story-point scale (say 10, 20, 40, 80, 160) as opposed to, say the fibonacci sequence (1, 2, 3, 5, 8, 13, or multiples thereof), it is a lot easier for your scale to satisfy the closure properties over addition and subtraction. In other words, with a geometric scale, a product owner can say “Hmm… I think this 40 point story is not ready to be played yet”, and you can respond with “How about we swap it with these two 20 pointers?” This could be a bit less intuitive when dealing with the fibonacci scale. All IMHO.