I have been looking at getting the first one. It's cheap, and works.
The first and second both have fans in the back, while the 3rd one appears to only have some slots on the site for air, without a fan. If you are going to run a hard drive, I suggest getting one with a fan because the hard drive will give off a lot of heat.
You might check Newegg to see what some customers have said about the models that are carried over there.