Flash is proprietary, expensive, and supposed to slowly be going the way of the dodo - particularly as HTML5 gains popularity. Already Flash is unsupported on new Android devices (which might be a good target platform for such an app). On the other hand, Python is free software, cross-platform, and is only getting bigger.
PyGame support for Android is increasing (albeit slowly) with projects like [this. Some indie game developers such as the developers for the Binding of Isaac seem to be in the process of [URL="https://en.wikipedia.org/wiki/The_Binding_of_Isaac_%28video_game%29"]rewriting their games](http://pygame.renpy.org/) to move away from Flash to avoid bugs and improve cross-platform compatibility.
If you're interested in releasing your game as free software and potentially getting other people on board to improve it, I expect Python will give you a much better chance of being successful in doing so. You may even be able to get your game packaged in the official Debian main (or Ubuntu universe) repositories if it's interesting enough - but that won't happen with Flash.
To answer your question, either language will do the job. If the above points are not a concern and you just intend to work on a small hobby project where your primary focus is to just get it done, the language of choice should probably just boil down to your own preference.