Well. Let me be honest with this. The question came to me years ago when I was interviewed by a panel. They told me that I will be ‘based in’ Delhi (in India). I wasn’t sure what the burly man on the other side of the desk meant, but I chose to keep quiet so as not to sound silly by asking a stupid question. It seems that there was not one.
I will explain what the two mean, and also detail how erroneously we use one of them. Yes, that means that one of the two, either “based on” or “based on”, shouldn’t really exist. You are aware of the variations in the English language that different cultures have brought. There was British English. Then came the Americans and Australians. The changes had to be introduced. Along with them he advanced in confusion as the world shrank. Diverse cultures meet, interact and exchange knowledge and resources.
“Based in” Delhi would mean the company is in Delhi. “Based in London” would mean that the company has its headquarters or main branch in London. If an interviewer said: “You will be based in London”, it would mean that the candidate will work in London. You will be asked to stay in London, to come to the office like everyone else. Generally, you will work in London. Easy. Nothing complicated.
‘Based on’ is a bone of contention. While it is commonly used in the United States, those in other countries are often not comfortable saying and understanding it. A phrase “You will be based in Delhi” would normally mean that the person will have to leave Delhi frequently, but the headquarters or main office will be in Delhi. Nowhere does it imply that the person will be required to spend most of his time working in the city.
In contrast, the British use “work out of” for the American “based on.” For me, “working outside of” fits more appropriately in this context. To make it simpler: it’s more about language differences and individual preferences.
Over time, the distinction between languages has faded and people have accepted both “working from” and “based on.” If you know your audience or readers, it should be easy for you to understand what to use. Now that you know how it differs from “based on,” you can use it appropriately.