PyTorch definitely makes experimentation much better. For example, if you want to train some system that is highly dynamic (reinforcement learning, for example), you might want to use a real scripting language which is Python, and PyTorch makes that really sweet.

Sometimes the line gets a bit blurred - for research that are focusing on relatively fixed patterns, such as Mask RCNN, both PyTorch and caffe2 are working great. In fact, Mask RCNN is trained in Caffe2, and that also makes things much easy when we put it on mobile - what our CTO Mike Schroepfer showed in his keynote is a Mask RCNN model trained and then deployed onto mobile with Caffe2.