When to use a Pure proxy with a Multisig

In what cases should you use a pure proxy?

A pure proxy is not multi-chain. Unlike most accounts in the Polkadot ecosystem, you can't use a pure proxy address on another chain than the one on which you created it.

Example:

You create a pure proxy with address 123...456 on the Polkadot Relay chain
⚠️ You DO NOT have access to this address 123...456 on Asset Hub
⚠️ you SHOULD NOT receive funds (UDST, USDC, DOT or any other asset) on this address 123...456 on Asset Hub because you wouldn't be able to access them

A pure proxy in front of a Multisig is useful to make it flexible. Thanks to a pure proxy, you can change the signatories of a multisig, see this video.
However, due to the limitations of pure proxies, you should only use one if the multisig you plan to have will not be used cross chain.

Conclusion

Do not use a pure proxy if:
❌ You plan to use the multisig on more than 1 chain (e.g Relay and Asset Hub)

Use a pure proxy if:
✅ You will use the multisig only on 1 chain
✅ You want to be able to change signatories