They are both the same thing. I am English, born in the UK and I always seen both ways in English. Even an English teacher would say that they are both the same. I like using "whilst" quite a bit but for me it depends on concept. For example, "while I was waiting in the queue". "Whilst I took the pencil out of my bag....". So I use whatever depending on the situation but it is the same if you are going to swap round the words. "Whilst I was waiting in the queue". I think whilst sounds more familiar to me though.