# Time series RNN vs DNN

Understandably RNNs are very good at solving problems involving audio, video and text processing due to arbitrary input length of this sort of data. What I don't understand is why RNNs are also superior at predicting time series data and why we use them over simple MLP DNNs.

Say I wanted to predict what the value in the time series is at t+1. I would take a window of lets say t-50, t-49...tand then feed loads of sampled training data into a network. I could either choose to have a single LSTM unit remembering the entire window and basing the predictions on that or I could simply make a 50 neuron wide MLP network. What exactly is it about RNNs that makes them better in this scenario or any scenario for that matter?

I understand that the LSTM would have substantially less weights (in this scenario) and should be less computationally intensive, but apart from that I don't see any difference in these two methods.