There is no comparison between both Bitcoin and Litecoin.Bitcoin is real and innovation and LTC was made after this.If you want to invest then Bitcoin is best and when the prices will rise it will have impact also on Litecoin too.
LTC is second only because it historically came after. It has several improvements, some of which are no longer relevant (attempted ASIC resistant mining), but some advantages such as shorter block times are not negligeable. It can be very frustrating to have to wait 20 minutes for a BTC transaction to confirm and complete. So LTC IS better than BTC; its just not as recognised.
That being said, I am discovering other coins with many more innovations over both BTC and LTC, so in terms of functionality these coins deserve an even better spot than the BTC. But at the end of the day, it is social recognition that has the last word...