There's something called dual channel where, as you guessed, it increases the speed basically when there are 2 sticks. However, it gives a VERY tiny boost in performance - about 5% maximum which is basically nothing.
You've also got to think that if you're adding another stick of RAM later, it's best to have 1 stick of double the memory.
TL;DR it doesn't really matter, 1vs2 sticks. Marginal performance increase with 2 sticks.