I noticed that a lot of people found this questions useful - so I turned it into an expert roundup.
I questioned people like Adam Houlahan, Sam Hurley, Erik Qualman, Ritchie Pettauer, Mandy McEwen, Tim Hughes - in total 38 experts.
In the end - I combined the data into an infographic:
The full article is here --> https://maxtraffic.com/blog/web-push-notification-roundup
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