glulam verses parallam/versalm
For a 28 foot span, you would typically hire an engineer or architect to design the beam, the connections, and the supports. They would select an appropriate type of beam based on the loading and aesthetic considerations. At that span, they might also consider a steel beam, or a truss, depending on available clearance. Typically a contractor is not going to be able to design the beam themselves, they would likely retain an engineer, since in most areas major structural renovations requires an engineer's stamp on the plans.
Contractors probably have personal favorite types of beams they are used to working with. There are many different manufacturers of laminated beams, and they sell their product with different names like Parallam or Versalam or LVL. In the end, it comes down to headroom, cost, and appearance, plus ease of installation.