We initially though we would use Django because it seemed to have a lot of the things we needed out of the box. After a bit of research we realized that using Flask would be a better option since it is more flexible and would be lighter for our purposes. Having set up our REST api using Flask we believe that we did make the right decision. We found that the flexibility of Flask along with the many extensions available for it to be very appealing. We were able to add the functionality we needed without much difficulty thanks to the quality of the extensions and their documentation.
Dane, if flask use extension, that means developer has to structure their own project. Do you know any good example or article in how to structure flask REST project
That's a good point. There is more you have to do but it also gives you more flexibility!
The Flask documentation is actually quite good and has some useful examples. Take a look at https://flask-restful.readthedocs.io/en/latest/ for the documention about Flask-RESTful