Selecting switching regulator components based on cost and performance
TI's Web Bench selects components (capacitors and inductors in particular) from parts offered from various manufacturers that have agreed to support TI's design tools. Generally they will select components based upon both a set of "rules" and best choice of specifications. 

As I recall the Web Bench tool used to let you select alternate  components and re-run the simulation to see how the component change affects the circuit efficiency, ripple voltage on output and various other parameters. 

In general you do not want to be just freely substituting components in switching regulator designs unless you are well versed in the technology and the nuances involved. Many of TI's switching regulator data sheets include a detailed design steps and calculations section to help with the component selections. It can be a good idea to follow through this process even though you have used the Web Bench designer to double check the components the tool selected for you.

I must say that the tools that TI offers and the high quality switching regulators that they sell these days make the design of a decent and well behaved switching regulator circuit a lot simpler than the state of the art some 10 to 15 years ago. But with any circuit like these a huge percentage of success comes with understanding how to make the circuit board layout in the correct manner. This is a skill that will come from experience and a failure or two.