my kegerator is a full size fridge, with a top freezer. it can hold 6 kegs, and i have six faucets coming through the door.
i also have two chest freezers with temp controllers on them for cold storage and fermenting, one is about 8 cubic feet, the other is 22 cubic feet.
what i'm trying to say is: get both!
in all seriousness, it depends on your situation. do you need a smaller footprint? if so, then a full size fridge would work better for you. if you want greater capacity, and don't mind making a collar, or drilling through the lid for a tower, then a chest freezer is for you. if you ever want to get a half barrel for some reason, a fridge is the way to go, as you do NOT want to be lifting a half barrel by yourself without any mechanical advantage.
so really, you need to give us more information regarding your situation. if money is an issue, a full size fridge can usually be found on craigslist for free (be careful though, they can eat through electricity), and chest freezers can be found for a good price every now and then. are you living in an apartment? home? how large is your home? how large is your beer area? how many kegs do you currently have? what size batch do you make, and how often?