Chest freezers will require the purchase of a temperature controller. The simple ones just plug into the wall and then your freezer plugs into the controller.
Advantages of a keezer.
1) More storage capacity.
2) Far easier to modify if you want the taps coming out of the top.
3) I personally think (even though I don't have one yet) that you can build a far more attractive end product with a chest freezer.
Advantages of a kegger.
1) Typically, but not always you can pick up a used refrigerator alot cheaper than a freezer.
2) Really easy to attach faucets to the door.
3) Bigger refrigerators can handle 4 kegs if you remove the door racks.
4) No temperature control needed.
5) Easy to load kegs in and out.
Make Beer, Not War.