We use parallels and VMware at work, VMware has one killer feature which I absolutely cannot live without...linked clones.
Although fusion doesn't let you create them within the GUI (which Workstation does), it does fully support them. Install windows once and create virtual machines from a snapshot.
This means you can create clones of a fresh installation at the drop of a hat and they don't take up much space as they use the snapshot as the base and only store the delta from that.
Also parallels seems to always start out VM's in coherance even though everywhere we tell it not too, that's f**king annoying.