Q: If the amount is the same, What difference does it make lifting free weights as opposed to machine weights?

A: Free weights are better than machines because they work all the little stabilizer muscles that don't have to do much with machine work. They also allow for different paths of motion working muscles from different angles and for working through different sticking point in the exercise. Finally they allow for compound exercises like deadlifts, squats, and lunges.

Of course if you do not have access to free weights, machines will still allow for great progress. And machines may be a good starting point for beginners since there's less chance of injury and they are in general less intimidating. But all other things being equal, I would almost always recommend using free weights over machines.