When you upgrade your vsphere and esxi versions you have a vmware tools and hardware version upgrade. Version 10 is called Compatibility mode 5.5 (good name change) does continue to force you on to the web client. If you upgrade to 10/5.5 you will be unable to edit virtual machine settings in the fat C# client. It does warn you but if your like me you just clicked right on through:
Followed up by this error:
So you have been warned get used to that web client.
Just for people new to the process you can revert the hardware version with a snapshot so take one first.