I would surely go for Ethereum over Litecoin for the reason that it is more popular in this industry. The reason might be shallow but if you are not new in this market, you would understand my point at the first glance. Popularity makes a crypto strong since its market value is dependent with the demand and supply. If a coin is popular, demand would be high as well as the market volume which makes it a better investment at this aspect over LTC. But still, LTC is a good coin. It is just that I believe that ETH is a better investment.
I like to invest in technology projects and Ethreum is the most suitable project for my long-term investment because the potential of this coin is expected to be very promising in the next few years. Currently what people are waiting for is about to happen and hope that after ETH 2.0 was launched, this coin will have many improvements. I don't know when the change will occur but ETH will undoubtedly return to the $500 someday.