they are almost identical. I would tend to use 'because' much more often. But due is usually used when you are trying to be more formal, or if you want something to sound 'official' or important! To give a real life example, I get sick and write an email to my boss: 'Dear Boss, I won't be able to come to work today because I am sick, Very sorry, Alex.' OR 'Dear Boss, Due to the fact that I have become sick, I won't be able to come to work today, Sincere Apologies, Alex.' I'd never write the second one because it's too polite even for work. However, it is common in some situations, like at the train station: 'Dear Passengers, please be aware that due to signal failures there will be a ten minute delay on all overground services today.' this is much more formal, but is appropriate in this situation. In fact, 'due to' has fairly negative connotations to me because it is often used by a company who is giving an excuse for something!

Due to works as an adjective, because of works as an adverb. I smell because of not washing My smell is due to not washing Many native speakers don't know this, but you need to if you want to pass your exams.

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