The app is the same, and the calculations are more or less the same. In fact, the app is based in the system of the old MERP red book. But they are very likely, the main difference are the critics that are received, that in the case of the app have to be made as if the character made a critic to a L 20 creature.
Anyway, the best option is to calculate the experience points by your own means and then do it with the app to check if the results are more or less the same in order to use the app or not.
