Bitcoin or Litecoin?

Looking for some advice on whether I should invest in Bitcoin or Litecoin.

Bitcoin has the brand and the distribution and I believe in it's future, but it seems to have some serious technological challenges ahead of it. The Litecoin technology is great but there is not much acceptance of it out there at the moment!

I read that Lee aims to enable bitcoin and litecoin to exchange seamlessly - which would certainly improve litecoin's usefulness.

I am about to invest some money and I already have some bitcoin but can't decide whether to put the extra straight into bitcoin or get some litecoin instead. As a long-term investment (say 5 years) what does everyone think about the difference between investing it in litecoin rather than bitcoin?

Thanks in advance for your advice,

Will