To compare multiple Proxy configuration differences from Management Center.
Management Center managing policies.
In Management Center you do have the ability to identify the changes between versions of policies; the feature is called 'Compare Different Versions of the Same Policy'. Here are the instructions, documented in the Management Center WebGuide:
https://origin-symwisedownload.symantec.com/resources/webguides/managementcenter/1.10.1.1/ManagementCenter.htm#ConfigurationManagementGuide/6_Policy/compare_versions_policy.htm?Highlight=diff policy