The simple answer is to use what you like. If Khan resonates with you, use that. If Emperor calls out to you, use that.
I have used both and Emperor is much more productive than Khan. Khan is more sexier than Emperor.
If a person wants to focus on his productivity while at the same time being a bit social with a bit of romance, they use Emperor. Plus, Emperor is very good for those who want to be solopreneurs.
If a person wants to heal his hangups regarding wealth and women, and be a force to be reckoned with in both domains, he chooses Khan. It is very good for leadership too and you won’t be too focused on going solo.
Emperor is suited for the introverted and those who want to focus on introversion for a while. Khan is excellent for extroversion and those who want to get into the habit of being more extroverted.
In a historical sense, you should also understand that Khan was the first multistage title made by SubliminalClub. For that reason it had most of the contents of the titles that came before it like Ascension, Mogul, Primal, Sex & Seduction, Emperor, Rebirth, etc. But that doesn’t mean that Khan has the full Emperor scripting.
Do you want Khan to remain the way it is? Maybe that is why you are asking this. Am only hypothesising though.
EDIT: am talking about current Khan. Not sure what the upgrade will be.