Disclaimer: my answer is not from linguistic perspective but from a native speaker, from daily use of the language. The meaning is same. Both mean "to do" as probably you know. I feel it natural to use やる for express what we are doing as an occupation or as our daily activities. For example, "I am a police officer" is 私は警官をやっています. It can be said 私は警官をしています. But for me やっています sounds more natural. Well, it is my answer, but I am not confident about my accuracy. Don't take my answer as definitive, but just an opinion.