I have not tested GRU cells on these problems. The GRU cells are not too different from LSTM cells--both models make heavy use of gating terms. As such, I don't

I have not tested GRU cells on these problems. The GRU cells are not too different from LSTM cells--both models make heavy use of gating terms. As such, I don't expect a GRU model to do much better than a LSTM. But I cannot say for certain, having not tried it.