Both uMatrix 0.9.3.6 and Ghostery 7.0.1.4 (Firefox 49.0.2) block the same trackers at https://www.security.nl. Should one of the two block the trackers first and then the other would not find any trackers at all?
Trackers that are displayed in uMatrix can be seen in Ghostery too. uMatrix doesn't "hide" them from Ghostery. If "google-analytics + googletagservices.com" are blocked in uMatrix but you allow them in Ghostery, they stay blocked. To allow them, you have to do that in both extensions at the same time. So you have more work to do if you run both extensions. Go to websites with a lot of trackers. If you see that Ghostery blocks the same as uMatrix, then running Ghostery is "redundant" because uMatrix is already blocking these trackers. But it depends on the filter-lists you have selected in uMatrix.
From what I've seen on my system is that most script-blockers will block the scripts before Ghostery gets a chance to. But Ghostery will still display all of the trackers, which is handy.
