I personally think the planning phase is the most important phase during a project. It sets the tone for the project and as Dr. Simon mentions if you fail to plan, you plan to fail. For instance if you have gone through the proper steps in planning and have a great plan, if something happened at the company and you could not move forward to the executing phase, you could potential outsource if you had a great plan and have another party execute it. If you have a poor plan and have the resources to move forward with execution, you might end up with lackluster product or processes. I do agree with @cdj24 that all parts of a project are important and that executing process is very important because this is where the project is performed including as you mentioned the information distribution, solicitation, source selection, and managing vendor relations. These are very important parts of the Execution phase, but I believe the Planning phase is the integral phase.