PyTorch vs. Tensorflow Fold
There are a couple of good threads on Reddit right now (here and here).

I haven't used either of these frameworks, but from reading around and talking to users I gather that support for dynamic graphs in PyTorch is a 'top down design principle', whereas TensorFlow Fold is bolted on to the original Tensorflow framework, so if you're doing anything reasonably complicated with Tensorflow Fold you're probably going to end up doing a lot more hacking around than if you're using PyTorch.