There are many pros and cons about the concept of hiring a contractor in order to complete a work or doing the work yourself. First of all comes the cost. On hiring a contractor you will have to pay him wages that is fixed and cannot be bargained while if you do the same work yourself then that expenses can be saved. Another thing is experience. The workers are very experienced in the job that you would ask them to do. They have prior knowledge about the work but if you try to do that same job then not only will your time be wasted there is no guarantee that the completed will be perfect or not.
Time is another factor that should be taken into consideration. Workers are meant to do their job but you are not meant to do their job. They will take much less time than you would and it is quite obvious that you would have other work. So after all these details it is better you hire a contractor rather than doing the work yourself.