Also chest freezers tend to be more efficient simply they contain the cold when you pen the door. On an upright freezer the cold air falls out if the freezer when you open the door.
I would generally recommend that you purchase an appropriately sized chest freezer.
Just to make the counterpoint...
Any keezer is going to be efficient simply because you do not open the door to get a beer, you pull the tap handle on the outside. The cold air can't fall out if the door isn't opened.
I have an upright freezer for my keezer, and love it. I fit four cornies on the floor, and use the top shelf and the shelves in the door to store cans and bottles. An upright will take up less floor space than a chest with the same cubic feet. Weather a chest or upright is easier to get kegs in and out of is probably a personal preference. Being tall, i'm sure the chest keezer would be no problem for me.
I got my freezer on Craigslist for fairly cheap. It isn't very old, so it's fairly efficient. Either way, the money i saved over buying new will buy an awful lot of electricity. Used the coarse adjustment to get it into fridge temps pretty easily. It also has an auto-defrost, which seems to cut down on the moisture in it. As far as drilling through coils, the door won't have any, so you're safe there, and by removing the interior rear panel on mine, i was able to easily identify where coils were on the back and safely drill a hole for a CO2 line.
Overall, i think chest vs. upright and new vs. used both largely come down to personal preference and what is available locally at the time you are looking. With uprights, do be sure you look for one with removable shelves though!
