Didn’t the FAA have an Ops Spec for commercial operators to use the MDA as a DA without adjustment IF the underlying OIS (1:34, IIRC) had been done and found clear?
How would you know that looking at an approach plate? So you think that an operator is going to do an obstacle assessment?
The DA has the 50' momentary descent, and the MDA does not.
The 50' mom descent can be a bit of a real challenge, given that you are on final, go to DA, then decide to GA...how many seconds the decision process, seconds to push TOGA, and seconds for the ac to respond on idle thrust....just how far has a heavy descended in that scenario?
The DA/MDA has been calculated not only by obstacles in the approach, but obstacles in the missed.
There are many parameters, but as soon as you start allowing guesses, it will keep getting lower and lower....