No difference besides UI. Muun dsoesn't have LNURL wallet nor NIP-57 zap support from my understanding. I use Alby browser extension to manage my nostr keys and as my primary zap wallet. I use Zeus since I can link it to my Alby wallet. When I am on Damus on iOS I can send zaps via Zeus wallet which is pulling my funds from Alby since Alby doesn't have an iOS app. Hope that makes sense!