The "best" buy is any one of them that actually works. With fairly minor differences, any are decent cameras, I think.
As I have said in the FSU forum, I think it matters much more who you are buying from than which specific camera.
That said, I think either any of the Canonettes or the Vivitar 35EE or ES are very good starting points.
You can't depend on your eyes when your imagination is out of focus.