MEH and SEHs each have their own applications that are best suited to either one or two engines based on risk and operational financial compromises.
However, to simplify the argument:
Operating over a hostile environment (an environment where no safe forced landing area exists - defined as an area where there is an expectation of damage or injuries to the occupants or persons on the ground); clearly a MEH with "stay up" performance is inherently more safe than a SEH.
That is the bottom line!
Any other discussion on this matter is just hot air and guff!
DB