Compare
Cosmos and Polkadot do not solve the same problem.
One lets each chain keep its own validator set. The other offers a relay that checks many chains. Interoperability is not one product.
The split
Cosmos, in the paper, is zones and a hub, with each chain responsible for its own consensus. Polkadot, in the paper, is a relay whose validators help secure parachains. A bridge between two sovereign chains fails with those chains' keys. A parachain fails with the relay's assumptions and capacity.
What not to conclude
Neither page is a ranking, a token view, or a statement about which network is safer today. Read the papers, then read the live clients.