Why is Pokemon White 2 better than Pokemon White?

Question

Pokemon White 2 (Ill call it PW2 to save space) is better than Pokemon White (Ill call it PW to save space). Why?

You are given a more reliable array of Pokemon to choose your party from as you progress through the Story. It also enhances the chances of catching Shiny pokemon.

So, if you have to choose, get both. That way you can trade your self many pokemon, and complete your Pokedex!