While Max Endurance and Max Range might not be much different on paper...in reality..if you end up over an Island and have to hold for 4 hours because the one runway is blocked...I doubt you will do it FL450...but something more realistic in the the teens....on the other hand, if you wanted max range, you will probably (in a jet) take it up as high as possible to maximize fuel burn(and TAS) and winds to get the best speeds....
Between the two, in the real world..one is about getting somewhere the other is just hanging up there as long as possible..