I’d say VMware and Hyper-V are similar in that they allow you to virtualize servers with stability and consolidation in mind. Where they differ is management, features, and price.
When it comes to security, it all depends on how you implement the product. Enterprise class licenses for VMware are expensive, but they give you Cisco-built virtual switching which you can manage as if it was real equipment. Microsoft doesn’t have the versatility of the virtual switching, but their virtual network is just as secure if you set it up right.
Basically if you build the product using best practices, security will less of a concern.