Well, BTC is growing by having business adopt it and through the building of a strong infrastructure on top of it. Advertising might help a little but just getting the name of Bitcoin out the public space isn't going to be suffcient for the public to truely embrace Bitcoin and use it as a currency. A focus on education is probably what would be required. And it's not an easy task to educate a public which has no desire to learn(of course some people do, but I think it's safe to assume the majority do not).
As far as LTC goes, I don't feel that Litecoin has shown any innovation or progress since 2011 when it was created. I don't see the much to the argument for Litecoin continuing to be a major cryptocurrency unless the development team seriously steps up and starts adding innovated features. Considering how many new and exciting technologies are coming out in the crypto space right now it's likely Litecoin is going to be left behind unless something changes soon.
I'm sorry, not to sound like an ass but where is all the BTC innovation? This is an old and stale argument. I can replace the LTC in the above quote with BTC and it has the same meaning.
The fact of the matter is that BTC and LTC work together. The devs work together, and even the P2pool code received a tremendous donation from the LTC devs/community (which everyone uses, everyone meaning coins not people lol). BTC and LTC are brothers, LTC just happens to be a year behind in just about everything, but still light years ahead of other coins.
BTC has lots of innovation. Coloured coins, Lighthouse, tons of third party applications being built on top of BTC. Yes, the core protocol evolves at a snails pace. But with BTC the community is so large that all of these outside features that work with BTC can make up for it. With LTC there is nothing as far as I know. BTC and LTC don't work together, I don't see that connection at all really.
On the other hand there are lots of altcoins innovating lightning speed. Adding features like crazy while LTC does nothing but collect dust.
Personally, I would love to see a push to modernize LTC and bring it back to its former glory. But I don't see anyone from the LTC community caring enough to start in that direction.