Comparing productivity between two methods or environments is easy. You have a programmer read and judge the quantity and quality of code produced one way, then read and judge the code produced the other way, and decide which you'd rather have.
Want a number, rather than a subjective judgement? Too bad. Want a manager to make the determination, rather than a programmer? Too bad. Want to compare two coders without showing both their code to the same judge? Too bad. Experienced programmers know what works for them, but don't expect any good studies.
Want a number, rather than a subjective judgement? Too bad. Want a manager to make the determination, rather than a programmer? Too bad. Want to compare two coders without showing both their code to the same judge? Too bad. Experienced programmers know what works for them, but don't expect any good studies.