These interesting results raise a question: is this just personal preference? Is there more? I think we're looking at a clear pattern.
Winners are those who tried more things than everyone else, who refined their initial ideas further than the others
But those who stand to benefit most from good UX *aren't* the beginners. It's actually the very best practitioners in the world.
And ultimately, that's how you win competitions or get papers published.
Using Keras means you're more likely to win, and inversely, those who practice the sort of fast experimentation strategy that sets them up to win are more likely to prefer Keras.