X IF MISSING / IF THEN ELSE

[EstebanD]

Hi, just a quick question: which function is more efficient between X IF MISSING and IF THEN ELSE in terms of calculation time?
As I understand it, if we consider two variables A and B, X IF MISSING(A,B) and IF THEN ELSE(A=:NA :,B,A) will give the same result. In this case, is it better to use one expression rather than the other?
Thank you for your answer.

[Administrator]

Probably X IF MISSING. Data variables are calculated only once before a simulation starts, so if you are running sensitivity/optimization, X IF MISSING will execute once, the IF THEN ELSE will execute every time the model is run.

[tomfid]

X IF MISSING is also more convenient if you have multiple data inputs in the equation.