When running Windows 7 as a virtual machine under VMware Fusion, you have the option of Sleeping or Hibernating from within Windows, or suspending the VM from Fusion.
All the methods ultimately serve the same purpose but achieve it’s goals differently.
Sleeping and Suspending were very quick and I suspect invokes the same function, as in VMware Tools calls the Sleep function from within the OS. Contents in memory are held there and the VM is frozen in it’s current state. Hibernation on the other hand dumps everything from memory into a file within Windows, then halts the system, where upon waking needs to read everything back from this file back into memory. This is what makes Hibernating take a lot longer to initiate and recover from.
In my experience i’ve found that Sleeping or Suspending Windows 7 is quicker.