The filter does not allow you to drill down into the Custom Objects, we have approx 300 objects this takes considerable time to run for the
Filter on Custom Objects prior to running a comparison similar to Salesforce Change Set, select the required object and fields to compare
Fred Webster commented
I would extend this to include filters on most metadata types pre-compare. If I know I have 10 pages, 10 classes and 3 objects for a given development effort it would nice to only compare against those.