I have read that you should stick with the same brand for all your rulers, the reason given was that different brands can be a hair off from one another.
I would take my favorite, most often used ruler, and check it against all my other rulers and cutting mats. This way you will know for sure if there is any difference that you must allow for when measuring and cutting.
I have numerous brands of rulers and there are always those that become favorites.
If some of your rulers are out of sync in their measurements, why would you continue to use them?
The old rule of "an inch is an inch" needs to apply to all manufactures of measuring tools.
Joyce