Cryptocoin security is dependent on:
Strength of algorithm
Distribution of mining resources
Difficulty
Network strength

Strength of algorithm:
Scrypt is so much more expensive in terms of resources to purchase, lower hashrate creates an upper bound of attack strength.
It cost so much more money to increase attack strength in Litecoin that it becomes a very strong wall against attacks.
Hashrate is not the measurement of strength. Hashrate * Strength of algorithm is.
Compare a flood of millions of gallons water to thousands of larger boulders. The damage done by the boulders can be more even though the count is less.

Distribution of mining resources:
The distribution issue is not linear. It's parabolic (high imbalance at low and high ends of spectrum).
High jumps from one technology to the next has the same effect as low difficulty.
High jumps balkanize the mining power in the hands of people who do not spend.
If big miners don't buy carrots via bitcoin, then the bitcoins are useless to carrot farmers.

Difficulty:
The difficulty is lower in litecoin right now, but in reality litecoin is the same as bitcoin 5 years from now because of the algo strength.

Network strength:
It takes less work to get the same security in litecoin as it does in bitcoin.
Scrypt creates a tough ceiling for new tech to overcome.
Bigger bat is just as good as faster bat in physics.

All in all litecoin is a more secure network because no new technology can come in all of a sudden and surprise the network and undermine security even if only temporarily.