It is also the hardest question to answer of all the them. Everything depends on the local jurisdiction and the submittal package prepared by the applicant. If a submittal package is carefully prepared and predesign and pre-submittal conferences are held between the applicant, their consultants and the local affected agencies, things can go quite smoothly.
However, again depending on the jurisdiction, even with a perfect submittal it can take longer to get your building permit approved than it does to build your project.
Some jurisdictions find it difficult to concentrate on simplifying the process. Instead the focus goes to making sure every detail is documented and in writing on the plans. This effort to protect themselves against litigation can block the ability to serve the public by moving the projects quickly through the process.
Projects usually go through review by several separate departments during the permitting process. These are: Building, Fire, Planning, Utilities, and Development Engineering. Make sure you make the reviewers aware that you are expecting a rapid turnaround on your project review. Be sure to keep track of the status at least once each week, by phone. Good luck.