The latest version of the VMware virtual platform, vSphere 6.5 Update 1, comes with interesting new features and improved capabilities that bring tremendous benefits for the network in terms of improved functionality, management, security, and more, which were not available in previous versions.
The entire upgrade process needs to follow a specific sequence and flow; first, all PSCs, then all vCenters, then all ESXis. But if you have more VMware products, the entire sequence could be much complicated. For more information, see KB 2147289—Update sequence for vSphere 6.5 and its compatible VMware products at https://kb.vmware.com/kb/2147289.