MSCS does provide a bit more availability than HA/vMotion. Have you also considered DFS - its a bit simpler than MSCS...
MSCS works fine with SRM. However, SRM does NOT require a shared subnet across sites.
These are different levels you are trying to compare. HA provides redundancy in situation of ESXi host failure.
MSCS provides redundancy at application layer. File cluster is not an ideal example, but if you have for instance SQL on MSCS you know that if active SQL node has some issues at OS or application level you can simply failover SQL server to another node.
Virtual MSCS will work with SRM provided that you have array based replication tools which might be very expensive.
The biggest drawback of MSCS cluster in virtual environment is that you have to provide RDM disks in shared mode, which makes vMotion and Storage vMotion absolutely impossible for cluster nodes. This significantly makes vSphere admin's life more difficult as you cannot upgrade/reboot/put in maintenance mode your ESXi servers hosting Cluster Nodes without affecting services running on cluster.
If you are still eager to virtualized your cluster I would recommend consider building virtual cluster using iSCSI initiators in your Vietual Cluster nodes if you have iSCSI capable storage. This way you will be able to avoid constraints of RDM disks in shared mode.
One more recommendation - start slowly, first try Physical - Virtual cluster so as to be sure everything works just fine on virtual node.
It is all worth doing it if you really need to use these physical cluster nodes for something else while moving file cluster to vSphere. Otherwise, I would say you won't have that many benefits.
Using iSCSI initiators in conjuction with SRM will make a setup even more complex, since SRM will not be able to manage disks accesssed via iSCSI from within guest OS and manual steps will be required during test / failover..
If you need to re-IP your VMs at DR site, SRM will change IP addresses of VMs themselves only, any cluster IP addresses will must be changed manually / via custom scripts.
I would recommend to use virtualized MSCS only if this is absolutely necessary.
Could you please provide the steps to manually changethe virtual IP of MSCS SQL Cluster.
Also direct me where can i find the script to do this.