this and this wrote:
according to usatf decathlon scoring calculator
12.5 100 is 556 pts
5:00 1500 is 560 pts.
So the sub 5 1500 is very slightly more difficult to achieve.
i think it is much harder to get a sprinter to run sub 5 1500. The reason is not so much physiological but psychological. They would not want to do the training.
But there are some distance runners who have great endurance but do not have any fast twitch fibers. Physiologically they
just can't go sub 12.5.
I believe you can convert fast twitch to slow twitch but doing the reverse is much more difficult if not impossible.
The decathlon tables arent a good indication of relative difficulty. There is a seperate IAAF points list for that specific purpose.
The original points charts for the decathlon set the 1000 points level for each event at the (at the time) world record. A slope was then chosen based on the subjective beliefs of a committee, not in an attempt to make each event equal at any points level other than 1000. These lines dont go through "the origin" on a graph. This has since defined the event and is the framework for how decathletes go about choosing what sort of training to pursue to maximize their points.
By contrast, the iaaf scoring was set up as an attempt to make 400, 600, 800, or any other points level "equal" in each event. There is of course some arguments to be made as to whether the formulas and actuarial tables used are perfect, but that is the underlying objective. These are updated periodically.
My point is, if you want to compare 5 flat and 12.5, the IAAF charts are what you shouls go to, not the decathlon charts.