[agibsonccc]

It often just comes down to project requirements. Eg, what kind of model is required? How hard would it be to build with tool x?

For example, a big reason why a lot of computer vision research was built (and sorta still is because of momentum) on caffe was pre existing model zoos.

A big reason why people choose TF (despite lacking dynamic graphs) is just because of existing community.

Requirements for both papers as well as industry will continue to evolve. Each framework will have their own trade offs.