All onchain only wallet apps are all the same, so using multiple onchain apps on mobile is dumb and useless. Onchain is exclusively for opening/closing LN channels.

Advantage? To be ready in any moment to make payments in many situations. If one wallet app fail or doesn't have enough liquidity you can switch instantly to another one.

If you are using only Green for example, you are limited to their functionalities. Also I am talking about LIGHTNING capable wallets not onchain only.