The smith machine is a significant tool to utilize. However, in the land of Bodybuilding and Powerlifting free weights are king. For your particular situation you should try using the smith machine when you are unable to find a spotter so you can train heavy without risking an injury. Incorporate smith machine bench press in your routine but do not neglect free weight bench press. You can alternate how ever you would like just make sure you do not just stick to smith machine for a long period of time or you will most likely lose strength when attempting to use the free weight bench from the lack of using your stabilizer muscles.