Both the two projects, ChainLink & Polkadot, are very potential and get the attention of the community, we can say that these are the two leaders in their own trend: blockchain application in enterprises & cross-chain transactions. However, up to now, ChainLink has had partners and is applied in practice, while Polkadot is still perfecting its ecosystem to connect many blockchains together. Based on factuality, I vote for ChainLink.