I'm aware of two thermsistors in the Prusia i3 Rework. Are they the same? And if not, how do you tell them apart?
This depends on how you ended up with your finished printer. If it was a kit, then there is a chance that the thermistors might be the same, however, even a kit manufacturer might buy parts that come preassembled as I could imagine being the case for the hotend.
To find out about the actual thermistor you would need to look up the spec sheet of the manufacturer of your printer or the individual parts, afaik there is no way to identify them by having them in your hand beyond identifying the resistivity and the coefficient type by using a multimeter.
You could, of course, check the resistivity for a whole temperature range to compare the table of your thermistor to the tables which are listed in firmware, but then you could compile your own tables right away.