I cant see that the world need more then one crypto currency. Im pretty sure if bitcoins prices drops, all the other crypto currencies drops too.
I hear Litecoin is faster, so it will beat Bitcoin when you are at a cafeteria buying coffee, in cases where you may have queues if you accept Bitcoins. Although, bitcoin is quite ok too, I have been buying burgers at a local shop with bitcoins once in a while and it seems to work as fast as my debit card. But still...