I didn't bother reading that blog (I don't like almost empty topics which forces forum members to click an external link) but to answer the question which one to choose, it probably depends on the type of NFT.

Those platforms on Ethereum are still more popular and have more user base when it comes to arts. If I want to sell an Ape smoking some shit, I'd probably choose Opensea.

If I want to invest in NFT gaming, I'd most likely choose a project on Polkadot because............high ethereum transaction fees.