I haven't looked into the Lightning/Stellar combo yet, but one thing that Lightning/Litecoin and Lightning/Bitcoin (and others) have is that you can abstract aw

I haven't looked into the Lightning/Stellar combo yet, but one thing that Lightning/Litecoin and Lightning/Bitcoin (and others) have is that you can abstract away which coin you are paying with, and which coin the vendor accepts. If all the LN implementations match, then I could, for example, pay with Bitcoin on LN to a node that will convert it to Litecoin at a given price, then will send that payment to the vendor's node who will accept Litecoin as payment. That gives a massive incentive for altcoins to support and match the Bitcoin lightning-network APIs exactly, as then it becomes much easier for them to gain market share based on their other qualities (like stability, security, decentralization, longevity, etc...)