It’s been about 2 years since I switched across to VirtualBox (when the shared virtual disks feature was introduced). In that time there have been loads of updates to the product. In the same time frame, VMware Server has had zero releases. I still get a lot of people writing to me about issues with VMware Server installations. I immediately tell them to ditch it.
PS. I’ve got nothing against VMware’s paid-for offerings, which do get updates. I just don’t see the point in using them when VirtualBox is free and works great for me.