There are several reasons why it's worth migrating to version 6.5 Update 1:

• A migration tool has been introduced in version 6.5 as part of the installation media to support and make the migration simpler.
• Migration to vSphere 6.5 Update 1 is now supported from vSphere 6.0 Update 3 and from vSphere 5.5 Update 3b.
• VMware vCSA 6.5 provides better performance and scale and includes advanced features such as native vCenter HA, file-based backup and recovery, and embedded VUM. The security level of the virtual platform has been incremented, introducing new features such as the encrypted vMotion, ESXi secure boot, and VM encryption. The management of the infrastructure is now performed with a responsive and easy-to-use new HTML5-based vSphere Client interface.
• vSphere 6.5 Update 1 is the final release that supports third-party vSwitch, such as Cisco Nexus 1000V, Cisco VM-FEX, HPE 5900v, and IBM DVS 5000v, and those switches must be migrated off prior to upgrading to any future release. The introduction of REST-based APIs makes task automation easier.
• Another good reason to migrate to the new version is the extended period for the General Support of version 6.5 that will now end on November 15, 2021. If your virtual platform still runs vSphere 5.5, be careful because the General Support for version 5.5 will end on September 19, 2018.
• In addition, upgrading to vSphere 6.5 Update 1 prepares the environment for the hybrid cloud solution VMware Cloud on AWS.