When comparing Growl vs Notational Velocity, the Slant community recommends Notational Velocity for most people. In the question“What are the best power user tools for macOS?” Notational Velocity is ranked 14th while Growl is ranked 18th.
Ranked in these QuestionsQuestion Ranking
Pro Support for a lot more applications than the default notification system
In addition to all the applications that other people have written that support Growl, Growl includes several 'Extras' that serve various functions.
Pro Ability to be themed
Growl comes with almost 20 themes pre-installed so you can pick what works best for you. You can also create and install your own custom themes.
Pro Sync with mobile phone via Prowl
Prowl is the Growl client for iOS. Push to your iOS device notifications from your Mac or Windows computer, or from a multitude of apps and services.
Pro Syncs with SimpleNotes or Dropbox
Pro Simple and minimalistic
The interface is clean and unobtrusive.
Con Feels a bit outdated
The last release was from 2011. Although due to its brilliant simplicity in doing what it's designed for, some might think there hasn't been any need for an update, as long as it still works with the newer OSs.