Because Kusama is built as a testnet for Polkadot, the technical functionality of both networks is the same. However, the founder of Kusama said that Kusama is like the unknown frontier where everything is undiscovered but offers more opportunities for evolution. Here are key differences between the two:
1. Update frequency
Kusama network will add new referendums for token holders to participate in voting more than Polkadot. The frequency is around 4 times more. Therefore, Kusama will significantly have more updates than its cousin.
2. Lower barrier
The minimum number of tokens required for participation in the Kusama network is significantly smaller than Polkadot's. That is why Kusama has more validators or parachain higher than Polkadot. Kusama also has a program called 1000 Validators to further boost the number of participants.
3. Use cases
While Polkadot is mainly built for applications that require stability and security like finance or corporate usage, Kusama is known for its speed for development. You can say that Kusama is like a laboratory where new applications or technologies are being tested.