I think you can not compare those 2 projects directly because they are two different things. Solana is a completely new and different blockchain then ethereum and has nothing to do with ETH at all. Polygon is a layer 2 solution which is built upon Ethereum in order to increase the transaction speed and to reduce the hefty fees of ETH. Both blockchain have transaction fees that are only fractions of a dollar at the moment so i think they are on par in that regard. Polygon can access the Ethereum virtual machine which means that Ethereum smart contracts are running on the polygon network also so here you have the full functionality of the ETH chain with lower fees.