When it comes to the discrepancy in the lengths of the two nines, the flow of play on the course also must be considered, particularly if you will be considering using two tee starts for regular or tournament play.
Having one nine that is considerably longer than the other, no matter what the par is, will make scheduling starting times a bit more complicated, as one nine will take more time to complete than the other, causing unneeded delays and backups when players cross over. You don't want to be building bad playing experience quality into the course.
If you are doing a design change or building a new course, by using a computer simulation program, the GCA and the course owners will be able to know well ahead of time how much length asymmetry in the nines is too much.