Online payment for ETH or LTC
===> Which one is the best ?
Most of the wallet provider accepts the bitcoin, ethereum and litcoin in all the wallet. So payment can be done with the any of the coin according to the receiver end possible payment option. As of now bitcoin also does not reached big to the retailers, online purchase and service stores.
In the mentioned option in your post. We can go with ethereum because this is more popular than the LTC.