Is there a page/document that shows a comparison of these products and features side by side?
Seems like there is some overlap and some features that are unique to each.
I recommend you post this to the Cisco Partner Security Community for more sales information and product features and comparisons.
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I don't have a comparison, but found that CWS multi-year licenses are EOL and the suggested replacement is Umbrella. So, not sure what to infer from this as the two solutions implement differently.
If you have access to Cisco Sales Connect - I would take a look at the below link for info:
Please note though Umbrella has moved on some pace so check in on current features - Certainly two key things recently have come out - 103 categories now supported (if memory serves but I know all CWS's ones have been migrated) and Umbrella can now operate as full proxy or intelligent proxy