When comparing SizeUp vs Spectacle, the Slant community recommends Spectacle for most people. In the question“What are the best power user tools for macOS?” Spectacle is ranked 36th while SizeUp is ranked 46th. The most important reason people chose Spectacle is:
Spectacle is licensed under MIT with source code available on [GitHub](https://github.com/eczarny/spectacle).
Ranked in these QuestionsQuestion Ranking
Pro Keyboard centric
SizeUp has user-configurable keyboard shortcuts for a set of pre-defined actions.
SizeUp is easy and simple to use without having to configure.
Pro Supports multiple monitors / spaces
Windows can be sent to different monitors and spaces. It can also be aligned as needed.
Pro Menubar dropdown for shortcuts
Learning a bunch of keyboard shortcuts right off the bat may be difficult to remember at first, which is why a menubar shortcut for the app exists with all the shortcuts listed.
Pro Free and open source
Spectacle is licensed under MIT with source code available on GitHub.
Pro Simple hotkeys
Spectacle offers easy-to-remember preset hotkeys.
All windows in Spectacle can be controlled with keyboard shortcuts, so no mouse is needed. This makes for a fast way to control windows.
Pro Low footprint
Spectacle only uses up 18-19 MB of RAM, which means there is not much overhead by using this app.
Pro Great UX
Spectacle is easy to use and configure. It's plug and play.
Pro Multi-monitor support
Con Nag window
If a license is not purchased there is a nag window (which suspends function) that pops up when loading the app (at user login). The nag pop-up is also summoned at certain time intervals and by performing a certain number of commands (manually or by keyboard shortcut).
Con No on-the-fly split screen window settings
Unlike some other tiling window managers, SizeUp has no way to change the size of split screen actions on-the-fly. Any time a user wants to change how much room on the screen a window takes up when using the split screen function, they will need to manually change the settings, which can be time consuming.
Con Breaks on macOS High Sierra / Chrome or Firefox
Doesn't support side by side windows.
Con Impossible to add new functions
While keyboard shortcuts can be changed for the available actions, there is no way to add custom actions which in turn limits the functionality of the app.
Con Limited window sizing capabilities
You can use 1/2 of the screen vertically and horizontally (divide into 4 parts). You can also use the screen in thirds too, but only the left and right third: you can't use the 1/3 in the center. There is no way to do a more granular distribution.
Con Not maintained
The software is free, but no longer seems to be maintained.
Con Doesn't work with any Adobe products
There are some apps like Adobe Reader that do not work with Spectacle. Basically, any app with a heavily customized UI that breaks OS X accessibility will not work correctly under Spectacle.