I think all means of communication should be used, here's how:
- The project manager must hold a face to face meeting with the client, preferably every 2 weeks for small projects, every month for larger projects.
- The project manager should update the client, by email, by the end of every week (Friday)
- The project manager should call the client, but only if the client responded to an email asking for more information. If the project manager feels that this his reply might be misinterpreted, then he should call the client to avoid confusion and potential conflicts.
- The project manager should immediately meet (face to face) with the client if there are major issues in the project.
In this day and age of collaboration, the client can check the project status himself by logging in to an online PM tool, provided the project manager has set up one for his project. In any case, the project manager needs to proactively and regularly update the client about the status of the project, regardless on whether the client can check the status by himself or not.