add table explaining differences

Author: pwseg

src/unify/unify-event-filtering.md

@@ -15,3 +15,12 @@ Event Filtering is useful when you’re sending a lot of different event types i
 - Filter out events from certain regions or user groups
 - Keep events in Connections, but exclude them from Unify
 
+Unify Event Filtering works differently from Destination Filters in a few important ways:
+
+|                  | Unify Event Filtering                    | Destination Filters                     |
+| ---------------- | ---------------------------------------- | --------------------------------------- |
+| Where it applies | Unify space                              | Individual destinations                 |
+| Filter scope     | All sources connected to the space       | One source for each destination         |
+| Filter action    | Drops entire events                      | Can drop or modify events and fields    |
+| Setup            | Created through API, visible in Unify UI | Created in UI or API                    |
+| Timing           | Before identity resolution               | Before events get sent to a destination |