I'm pretty happy with the performance of my 13" Macbook Pro (MBP) with touch bar. The 3.1Ghz model is a big jump in technical specs for not a huge amount of additional costs. The 16GB of memory is certainly useful depending on what you're running, and data is constantly getting bigger (multi-band, multi-echo, etc) - so some amount of "future proofing" is good if you can afford it.
Any of the 15" models should be fine as well. Screen size can be a personal thing, if you want/need screen real estate and don't mind a larger package, absolutely go for it. The 15" model has more processors, so you'll be able to do things faster.
