Free Weights and Stabilizer Muscles
Free weights employ the stabilizer muscles more than machines. The more balance required in a movement, the greater the activation of the stabilizer muscles.
Step Ups Vs Squats
Step Ups engage more of the stabilizer muscles than squats. That because of the balance issue.
Squats Vs Hammer Leg Press
Squats involve more stabilizer muscle activation than the Hammer Leg Press, any leg press machine.
Engaging The Stabilizer Muscles
Thus, free weight are much mroe effective and should be employed as a means of working the stabilizer muscles.
The Downside of Free Weights
The downside of free weight is that the stabilizers are the weak link in the exercise.
Squat Example
The weak link in the squat is the core, specifically the lower back.
That means squats rarely completely overload the legs. The lower back give out before legs are completely overloaded.
Machines (Hammer, etc) and Stabilizer Muscles
Machine pretty much elimiated the use of stabilizer muscles.
You can have someone who is able to squat a ton on the Smith Machine or peform heavy leg press' but can squat that much.
Thus, the downside of machines is that your stabilizer muscles are not worked.
The Upside of Machines
The downside of machines is also the upside.
Machines allow you to completely overload the primary muscles involved in an exercise.
Leg Press vs Squat
One of the things the leg press does is eliminate the stabilizer muscles.
That allows you to completely overload the legs.
Tools
Think of free weight and machines like "training tools".
While you can hammer a nail with a crescent wrench, a hammer work a lot better.
That same thing applies with training exercise and methods.
Summary
Free weights and Hammer Machines (machines) each provide a different training effect.
The inclusion of both will enhance your training results.
Kenny Croxdale