There is basically no lock-in to any virtualisation platform these days. They all use essentially open virtual hard disk formats and it's trivial to convert from one to the other. But you end up locked in anyway, as all your scripting & management is targeted at whatever platform you choose - be it KVM/vSphere/Hyper-V. So choose the one that makes managing it easiest for you. If you like bash, choose KVM. If you like PowerShell, choose Hyper-V or vSphere.