Using free weights for compound moves is always better than using the smith's (unless you old or have some long term injury or something). The same amount of weight on a smiths aint the same as using a barbell. There's a lot of small muscles and CNS stimulation involved in just balancing the weight and keeping the movement smooth.You didn't explain what's better about this
SO the free barbell is superior. Stopping shy of a real struggle rep on the barbell is better than training to failure incessantly on the Smiths for 90% of people.