uhh i am a him and no i did not end up giving the dying mantis to my female as i just gave it a water burial and flushed him
Back to your original question, Massaman! As you know, mammals have a feedback sytem that responds to fullness of the stomach (the stomach doesn't have to contain useful nutrients, merely be full), mediated by a part of the brain (hypothalamus?) called the appestat which"tells" us when to stop eating
Insects have a much more complex food intake regulatory system, and opportunistic predators, like mantids, who have to eat as much as they can when they can, can store very large amounts of food in their crop (foregut). They will stop feeding when full, and also when about to molt or, sometimes, about to lay eggs. Note that the appearance of fullness in a female is often due to a large number of eggs and the proteinaceous material in the abdomen.
Not quite sure what you mean by "better food," A. Protein, protein and more protein seems to be the path to success for a female mantis's fecundity. There have been studies that suggest that a female who eats her mate after mating will be more fecund, but I know of no studies that show that such a meal is more nutritious than, say, a cricket (a cigarette can be nice, too
).