I was wondering which method is more accurate in terms of sizing from your experience
Accurate? What do you mean accurate? How separator ID may be accurate or inaccurate? Separator has two features only (1) it works as intended or not, (2) how much money you spent.
How much money you are ready to invest and which process cases this separator will unable to treat - this is the right choice of calculation method. It is an engineer's skill to define those conditions properly.
Edited by shvet1, 04 December 2023 - 12:12 AM.