I would probably pick Litecoin for long-term investment. This coin has shown some stability and reliability during all the drops of the market. I think it is a good choice to put your money in.
It's hard to say which coin will prove better in the long run. But at the moment I would prefer the ethereum, this coin is the most popular and reliable. A lot of projects are based on the ethereum!
I think that Ethereum will be better in the long run. But I have invested a lot in Litecoin too. It is good coin and it is very promising, just Ethereum is better.