I found two techniques for estimating user stories:
by the size of the story, which is unit-less
by the time estimate, which is measured by days
The first uses relative comparison between stories to infer time, and it should be independent on developer experience, while the second depends on developer experience.
I tried the first which is good, but I believe the second is more developer-friendly, and I want to see the pros and cons of each of them from practical experience. Any idea?