Token & Model
Polkadot’s native token is the DOT token, and the protocol relies on a sharded, pure-abstract STF model.
Cosmos’s token is an ATOM, and its model is the bridge-hub.
Polkadot’s consensus protocol is fast-forward.
Cosmos’s consensus protocol is Tendermint.
Block Production Sub-protocol
Polkadot’s block production protocol is Babe.
Cosmos is monolithic so it does not have a block production sub-protocol.
Finality Gadget Sub-protocol
Polkadot’s finality gadget sub-protocol is Grandpa.
Cosmos is monolithic so it does not have a finality gadget sub-protocol.
Main Chain Name
Polkadot’s Main chain name is Relay-chain.
Cosmos’s main chain name is Cosmos Hub. 
Interior Chains Name
Polkadot’s interior chain name is parachain.
Cosmos is not sharded, so there is no interior chain.
Exterior Chains Name
Polkadot’s exterior chain name is Solochain.
Cosmos’s exterior chain is called Zone.
 Technically, there’s little to prevent other “main chains” on the network if they can get enough buy-in.