The processing time for IR-1 and CR-1 visa may be almost double the period for K3 visa. The reason is the fact that IR-1 and CR-1 visa undergoes immigration processing before it is issued. The alien spouse will enter the United States as a U.S. Permanent Resident.
The K3 visa has shorter processing time but it will probably take the immigrant longer to obtain U.S. permanent resident status. This is because the alien spouse has to go through Adjustment of Status in the United States. Adjustment of Status can take up to six months to process. The benefit is that the alien spouse is in the US while waiting for the result.
To start your application for Adjustment of Status, please follow this link.