What's the pro cons of free weights vs weight machines?

Been hearing lots from various people - some professional trainer at the gym, some fitness freak, some not so fitness freak.

Considering I have no one to spot me at the gym (I go alone T_T), and I do weight machines (impression is it's safer to me, and the gym trainer commented it's perfectly fine to just do weight machines) - i still do hear from lots of people weight machines are rubbish

Lets hear some opinion

This topic has been discussed to death everywhere on the internet, including this section.

Just one example, Machines vs Free Weights