How to explain why Story Points are better for estimation using a little story:
My Ideal Days Are Not Your Ideal Days
Suppose two runners, one fast and one slow, are standing at the start of a trail. Each can see the whole course of the trail and they can agree that it is 1 kilome- ter. They can compare it to another trail they’ve each run and agree that it is about half the length of that other trail. Their discussions of trail size (really dis- tance in this case) are meaningful. Suppose instead of discussing the length of the trails these two runners dis- cussed the time it took to run the trails. The fast runner might say, “This is a six- minute trail,” to which the slow runner would respond, “No, it’s at least a ten- minute trail.” Each would be right, of course, but they would have no way of set- tling their differences other than agreeing to always discuss trails in terms of how long one of them (or some other runner) would take to run the trail.