[mixmastamyk]

As said I default to deferred %. That leaves judgement for need vs cost of call vs frequency, etc. Also f-string is faster than others with own via instruction, more readable, less likely to throw a runtime error. Judgement call.

Bottom line, still a micro optimization on a modern machine in the vast majority of cases.

If you have a truly costly format op and still want to use fstring, look into .isEnabledFor().