Even NetApp will usually tell you not to use RDMs unless you have a really good reason for doing so (MS Clustering and needing to use SnapManager for SQL would be the reasons they would give).
Connecting the iSCSI lun from Windows using Microsoft iSCSI would be the least complex solution, but using iSCSI RDMs connected to your ESXi hosts and connecting those to your VM as a virtual disk should offer better performance, with the benefits being more obvious if your database is heavily utliized (less processing within the VM, and if you have a hardware iSCSI adapter or if your NIC has iSCSI offload capability, you can take advantage of that, and you can balance the load across multiple NICs).