Need help comparing the 13" 2016 MBP with the 15" 2015 MBP
This really gets down to personal preference and in that sense your question will invite people to express opinions, rather than providing an answer to a problem.

The best way for you (and I dare say anyone) to make a decision is to identify what are the most important requirements for your intended use. For example:


CPU - The 15" mid-2015 MacBook Pro has a 4 core processor, while the 13" late-2016 MacBook Pro only has a 2 core processor, so if processing power is critical the mid-2015 model is a better choice.
Battery - The 13" late-2016 MacBook Pro, by virtue of its smaller screen size, will run longer on battery than the 15" mid-2015 MacBook Pro, so if running on battery power is critical, the 13" model is a better choice.
RAM - The 13" late-2016 MacBook Pro you're considering has 8GB RAM, while the 15" mid-2015 MacBook Pro has 16GB RAM, so if the apps you run are memory hungry, then the mid-2015 model is a better choice.
Display - The 15" mid-2015 MacBook Pro has a 15" screen (obviously) which has a native resolution of 2880x1800 pixels, while the 13" late-2016 MacBook Pro only has a 13" screen 2560x1600 pixels, so if the amount of desktop real estate is critical the mid-2015 model is a better choice.
Weight - The 15" mid-2015 MacBook Pro weighs 2.04Kg while the 13" late-2016 MacBook Pro weighs 1.37Kg, so if you're going to be carrying it around a lot, then the 13" model is a better choice.
Ports - It's well documented that the 13" late-2016 MacBook Pro has four USB-C ports and a 3.5mm headphone jack. The mid-2015 model on the other hand has two USB 3.0 ports, two Thunderbolt 2 ports, an HDMI port, an audio in/out port, and an SDXC card slot. Only you can decide which one is a better choice for the next three years!


You get the idea. Basically you need to decide your most important requirements and then do a comparison based on that.