Assuming this [1] is the main source repository for webapp2, it hasn't had any serious development since early 2012 and there's probably no reason to use it.
[1] https://code.google.com/archive/p/webapp-improved/source/def...
[1] https://code.google.com/archive/p/webapp-improved/source/def...
I also probably didn't formulate my question well. I didn't ask whether to use it or not, but how it compares to Flask - .