Fail Over Engine is better than VMotion

All our engines are running on VMWare clients and have VMotion enabled. We currently have engines deployed across three sites, but the VMotion at each site is constrained to that site and in a site DR scenario the failed servers would have to be restored from snapshots.

I desperately need detail and facts as to whether VMotion or FOE is better at protecting the Orion complex. Is there a paper on which is better or are there any case studies yet?

Many thanks

Robert