3D Printing ABS vs PLA... which is better to use?

http://uncrate.com/stuff/3doodler/

I know it may be a very long time before I can afford an actual 3D printer in my library. However, ever since I attended Engadget Expand I have been excited about a product I saw there called the 3Doodler which extrudes a single strand of plastic and we can actually draw with it. I have been following the progress of the 3Doodler which is expected to ship in April and may be a good low cost option to get 3D Printing off the ground in the library. But I have not order one because I am so confused as to which type of plastic I should be using. I may only get one chance to make a choice and this video goes a long way to help in my decision.