I'm an advocate of litecoin, as far as I'm concerned It's a pretty big ocean out there better we have an armada of ships sailing together in the same direction rather than all being on a single Bitcoin boat which to me sounds pretty cramped and an isolated target.
I think Bitcoin is great and don't want to see any litecoin success at the expense of it but having only one single blockchain out there is completely shortsighted. It's not viable to have thousands of competing CryptoCurrencies the altcoin bubble has burst but a small basket of complementary ones is completely reasonable.
In future if development of a coin isn't to your taste at least you can vote with your feet without have to head back to fiat, that cannot be said if you follow the 'only Bitcoin' mantra and is at least one good reason why Bitcoin holders should consider having a small investment in litecoin.
Right now the biggest things going on for BTC are basically:
1) Being the original altcoin: Has higher status than the rest of alts
2) Has a better and faster transaction time.
Unfortunately for LTC, BTC is going to increase its blocksize limit in the next update, which means Bitcoin will be faster than ever, therefore is one less thing that makes LTC worth it above BTC. Right now if i was holding LTC; I would keep holding it until the next pump (if it happens) because it truly cannot get any worse.