Since GRUs are relatively new, the question usually arises as to which network type to use and when. To be honest, there really is no clear winner here, as GRUs have yet to mature, and LSTM variants seem to pop up every month. GRUs do have fewer parameters, and theoretically may train a bit faster than a LSTM. It may also theoretically need less data than a LSTM. On the other hand, if you have a lot of data, the extra power of the LSTM may work better for you.