If you have a habit of leaving your lights on, or pack a monster stereo setup, you probably want a big battery. However, there are three reasons why you might not want the biggest and most powerful battery:
First, it may weigh more.
Second, the battery may cost more.
Third, the battery may discharge at a higher rate due to larger plate area.
My first concearn would be to get a high quality battery. I have a couple of old Panasonics in the shop that just refuse to die. I have no idea where they can be purchased, but they indicate to me that there is a difference in battery quality. I'm still using my 4 year old original Furukawa (or whatever it's called). The 12 volt battery only starts the car in extreme cold. (Having synthetic oil in the engine helps it crank over on these occasions)