Polygon has better scalability over BSC and it's also getting adopted by more and more defi and NFT related projects. Polygon can be a rival to the BSC as it has become a rival since the polygon smartcontract went live a few months ago.
If you're watching both since Q1 of this year and you would be seen a fight between BSC and polygon although polygon was a new smartcontract platform at that time it shows very good growth just like BSC. the only thing that make it different if polygon didn't get support from the biggest exchange site in the world. I mean binance was also contributing a lot to the BSC ecosystem as it has hundreds of thousands of user bases. it can be instant marketing when binance was announcing its new service to be added to its ecosystem but i guess polygon was the most potent competitor against BSC. Polygon has very big potential like BSC. The time will tell us. TVL on polygon was also slowly growing too.