I like to use free weights because it uses more muscles to keep the balance and works out more than just isolating one muscle group.

But then I would move to the machines during my workouts to make sure I isolate those particular muscle groups during my session.

I feel that doing both during my work out helps with my core when doing free weights and then I can really push the muscle group I;m training that day with the machines.

especially machines that allow individual movements for example you can pull with one arm at a time. That means I can mold my body to whatever shape I want.

If I feel weaker on my left then I'll work on it more