iSCSI vs SMB Performance

The use case for which these three NAS are being utilized as iSCSI targets is under VMware, where multiple hosts in a vSphere cluster are aware of the iSCSI targets and can access them as needed over the network. Migration between the NAS via iSCSI seems / “feels” (experientially) somewhat slow, and so I was wondering if there were any stats online from anyone doing speed tests in the past that might confirm SMB would be faster. I can switch the units over to SMB.