With calculated you never know what your oil pressure really is, the only real sensor you have is if you oil pressure gets down to 8psi (I think that is what the low sensor is set to). To me by the time you get down to 8 psi the damage is already done. Actual is when you either have a sensor that senses what oil pressure is being put out by the engine or a mechanical line directly to the engine that shows the pressure.
Im a old guy that has built a lot of engines in my life and on a lot of things I'm old school, I want to know what is actually going on in my engine not what the computer thinks is going on.
Im not saying its good or bad, just personal preference.
Tom