When comparing Fantastical vs AdAway, the Slant community recommends AdAway for most people. In the question“What are the most useful Android phone apps?” AdAway is ranked 2nd while Fantastical is ranked 19th. The most important reason people chose AdAway is:
Use the hosts files to block ads, so it works for everything.
Specs
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Pros
Pro Supports multiple calendar platforms
If you're locked into using an Exchange account, Google Calendar won't work without 3rd party syncing options. Fantastical works flawlessly with Exchange and with Google Accounts so you can have both. It also supports iCloud, Office365, Yahoo, and Facebook calendars.
Pro Fantastical can comprehend natural language
You can copy and paste a line from a meeting note and Fantastical can copy down and present the relevant information
Pro Beautiful and highly polished design
Pro System wide blocking
Use the hosts files to block ads, so it works for everything.
Pro Doesn't consume CPU time or memory
The app updates the hosts file periodically but doesn't need to run in the background in order to block ads, which is especially convenient for older phones.
Pro Can use systemless host
Can be used without modifying the system if rooted with magisk.
Pro Can use custom host files
Lots of people and keep their own updated host files used for blocking ads and ad away supports loading them in or even adding their source for autoloading.
Cons
Con Expensive for a single utility app
Fantastical on OS X costs $49.99 and an additional $4.99 if you want to use it on iOS.
Con Only supports iOS and OSX
Fantastical doesn't support web, Windows or Android.
Con Needs root (by design)
Needs root to update the hosts file.
Con Won't block same domain ads
Because the host file can only redirect domains, if the ad and content are on the same domain the ad will be displayed.