More or less storage?

Hi, I am looking to buy the Apple MacBook Pro with Retina (MGXA2LL/A) Laptop, 15.4". I am not sure if I should go with the "2.2GHz 4th Gen. Intel Core i7, 256GB Flash, 16GB DDR3L RAM, English" or "2.5GHz 4th Gen. Intel Core i7, 512GB Flash, 16GB DDR3L RAM, English." I am a university student who would be using it for word documents, emails, music and photos along with video streaming. I would like to know the difference and which would be more sufficient for my needs. 🙂 ps is retina display a must have?