Flask has a bigger dev team, but Bottle is a nicer, more elegant micro-framework. From what I can see, the design of Flask can be broken down into 2 phases.

Flask has a bigger dev team, but Bottle is a nicer, more elegant micro-framework. From what I can see, the design of Flask can be broken down into 2 phases. The first phase is essentially like bottle. The second phase added class views and the likes. And it became inelegant and verbose. If bottle has something like Flask's Blueprint, which facilitates the management of larger projects, bottle will clearly win as a micro-framework. In the end, who is the winner really boils down to how much love a framework is given to by its founder. Web.py started a generation of nice frameworks, but I think the person behind it didn't put a lot of effort in pushing it forward, and eventually, it just stopped progressing.