Load, Compare & Diff Registry of Windows Servers & Clients on VHDs?

We are deploying various Windows Servers {2008, 2012} & Clients {7,8.x, 10} and various custom applications, versions & special utilities.

Without bothering the audience here on specifics of each, we'd like to figure out what tools/ ways could we use to do a 'compare / diff' between the entire or partial registry of various online/ offline instances of these machines.

We can use Beyond Compare to file / folder diff compares between 2 instances, but not sure what can help load & diff/compare between registries of 2 VHD/ machine instances.

If you don't mind Linux, I'd really recommend winregfs. It transforms the hive file contents into plain files and folders that can be accessed and handled by whatever your preferred diffing tool is.

Otherwise depending on your level programming expertise I guess you could hook into one of the many libraries for the task, or just use a NirSoft GUI.