Which feature would allow for the non-disruptive migration of a virtual machine between two clusters...

vSphere vMotion allows for the non-disruptive migration of a virtual machine between two clusters in a single vCenter instance, as long as there is shared storage and network connectivity between the clusters.

References: https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.vcenterhost.doc/GUID-3B41119A-1276-404B-8BFB-A32409052449.html

vMotion is used to move the VM to a different cluster within the same vCenter. This only works if both clusters share the same storage. If they don't you also need to perform a Storage vMotion. Cross vCenter Migration is only used to migrate to a different vCenter.