Individual hedgehogs seem to have different temperature preferences. Unfortunately, I don't think you can figure out what your particular friend's are without accidentally going outside them and having a hibernation or estivation attempt. This particular experiment is not recommended! To avoid accidentally conducting it, most people suggest staying in the middle of the range, thus the high minimum temperature (Tom's 72-75) and low maximum temperature (Tom's 78).
Now, my particular hedgehog does not like very high temperatures: he starts radiating hedgehog-misery and overheating around 78, and by 80 he's looking at me like I've personally betrayed him. I'd rather not find out what his lower-limit temperature is, but he's totally happy at 72, so that's where his thermostat is set to click on. I've read about other hedgehogs on the forum who absolutely have a higher temperature happy-zone than him, particularly after they've attempted hibernation or been sick.
Part of the idea is that it's not just the temperature, but change in temperature, that can lead to hibernation attempts. I live somewhere with a cool to cold ambient temperature (we consider it a crazy heat-wave if we get to 80F outside), so I can have a lot of confidence that if I set a lower-bound temperature, the outside world won't go above it. For someone living somewhere that's naturally hotter (I'm looking at you, Florida hedgehog-owners), the year-round ambient temperature is much warmer, and if it goes through a cold freeze all the way down to 70F, little hedgehog might attempt hibernating. So in those circumstances, setting the thermostat to a higher baseline minimum so it clicks on and keeps the temperature stable near the average, even though it's higher than the minimum, would be a good idea.
Does that give you a better idea of why the ranges can be so big, and how to figure out what a good temperature for you and your hedgehog is?