If you're genuine about your goal (re-examine your own feelings, it's easy to deceive oneself!), your question is going in the wrong direction.
The framework doesn't matter.
If you want to release a startup quickly, just do the minimum amount of work to test the hypothesis you have about your user. Most of the time that will not involve programming. It could be as simple as setting up a Gform or calling a few friends and talking to them about their problems.
If it turns out you do need to code, take whatever tool you already know that gets the job done. Crucially, "gets the job done" means: focus only on what you know you already need. Do not plan ahead. Don't think about scalability. You can always re-write if your idea is actually good (which it almost never is).
Do things that don't scale.
However, if you find your motivation is not so much about starting a startup, but more about learning a new framework, just pick the one that's most interesting to you.