Pynecone is specifically designed for web apps and I think it does better on more complex, larger web apps. This can be seen in Pynecone's main website being made in Pynecone and while Flet's website is made in JS not Flet. Both are good frameworks and Flet has advantages of creating mobile/desktop apps because it compiles down to flutter while Pynecone is great for web because it compiles down to nextjs/react frontend.