I live in a country that doesn't have English as its main language. I have two choices in writing, either write in my mother language or write in English.
Why should or shouldn't I write in English?
My first few thoughts were:
Do publishers often publish works that are not in that country's language?
More people speak English, so one would assume you have a bigger audience in English. But, it is also logical that it is easier to connect to people in the same language and it will gain readers faster.
Of course, language skills are also an issue. What level of English would be acceptable (and editable) for publishers? Where would they draw the line and say, no, this is too awful?
Is it possible to publish a book in a country you don't live in, but it's an English-speaking country and so better suited for an English book? How do publishers address this? Do they pay attention to country when getting a manuscript?
So, to summarize, I think it would be a good idea to generate a list of pros and cons so people thinking about writing in English instead of their main language can read it and make a better decision.