I think in this case it boils down to whether you ever need to do a pattern match over the select box type. If you do, then having the compiler check for exaust

I think in this case it boils down to whether you ever need to do a pattern match over the select box type. If you do, then having the compiler check for exaustiveness makes the code more robust. If all you care is the string representation of the strings and how they convert to a numeric time then a dictionary will do the job just as well, while keeping things simpler.