Setting a variable conditionally using the calculation engine is faster than using script step conditionals, according to my tests.
In other words,
Set Variable [ $variableName ; If ( condition ; trueValue ; falseValue ) ]
is faster than
If [ condition ]
Set Variable [ $variableName ; trueValue ]
Set Variable [ $variableName ; falseValue ]
The difference varies, but in the script shown in the attachment, the advantage is about 33%.
I wasn't sure whether this would be the case based on what I could discern from the documentation and other forum threads.
I suppose this means there is a noticeable tradeoff between step-by-step visibility and conditional evaluation performance in this case.