VirtualBox is cross-platform; runs on Linux, Mac, Windows. Images are portable. As a sibling notes, the Windows built-in is Hyper-V. Or if you don’t like your money, VMWare.
The free player is what earlier on was the normal version of Fusion.
So you only lack the professional features like connect to a vSphere host, have the network editor and a few other smaller issues.
See the Compare tab at [0] for a complete list.
edit:
Oh.. and if you meant VMware Workstation Player then see this list [1]