Processing times will vary from service center to service center, from form to form, and for each U.S. Consulate. Furthermore, processing times vary and can change without notice! Current processing times, according to USCIS, for I-485 applications at the CSC are 4 months, but, again, that is only an estimate. It still may be helpful to make an inquiry to the National Customer Service Center (be nice in your inquiry!).
Both processes should take about the same time. It is likely that your I-485 application should be approved soon unless there are issues with the application that are being investigated.