if you are using 10 gig for vmotion and management it will be very good, you can have 8 concurrent vmotion and with multinic vmotion the speed is very very good.
regarding the cloning, you have to look at the storage array performance, the datastore iops usage and load. the array latency, and the array is capable of VAAI..this will offload many of the storage over head from vmware esx kernel to the storage controller.
so check the array performance, and also open a ESXTOP and see the DAV/GAV latency or use vcenter performance section to see these array latency