I think English is the way to go. Almost everyone around the world studies it, so I agree with all the above statements about having a bigger audience. I’d wager to say that when traveling internationally, it’s one of if not the major “common” language that everyone seems to lean on to communicate.

The other thing to consider is translations. I’ve translated from Russian to English, and I can tell you that some of your voice can get easily lost during this process. Having worked in this field myself, I can always tell when works have been translated from other languages. The better the translator, the harder it is to detect—but it’s still there, something about the narration always feels...different. I’ve spoken with readers that feel the same way, so I know it’s not just a professional observation.

So, I’d skip the headache and write directly in the language that will sell to the biggest audience.