The type of contractor you should hire depends on the type of work you are looking to have done. If you are only looking to change one element of your home, such as replacing the windows, you may choose to only hire a subcontractor. If you plan on having more work done, and you are going to need more than one subcontractor working at one time, it may be a good idea to hire a general contractor.
The general contractor will be able to manage the subcontractors so that they are working cohesively and to the right timescales. When I chose to have a sunroom built, I decided to hire general contractors in Dartmouth, MA to oversee the project and manage the subcontractors because I was aware that I would need a few different contractors to perform the necessary tasks like painting, installing windows, and bricklaying.