When comparing ShiftIt vs Better Touch Tool, the Slant community recommends Better Touch Tool for most people. In the question“What are the best power user tools for macOS?” Better Touch Tool is ranked 32nd while ShiftIt is ranked 46th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Easy to configure
ShiftIt is configured through a simple UI where you simply press the hotkeys you wish to map to a certain action.
Pro Free
Pro Intuitive
ShiftIt is very straight-forward to use for most frequent usages.
Pro Open source
Pro Configuration can be committed to your personal dotfiles repository
Configuration winds up living in .hammerspoon/init.lua and .hammerspoon/Spoons/ShiftIt.lua. Very easy to track configuration changes.
Pro Endlessly customizable
Pro Extendability
Allows user to extend my MBP with touchbar by creating custom actions per app. Also supports system-wide integration (touchbar actions).
Pro BTT makes it simple to sync your hotkey, Touch Bar and gesture setup between several machines
Pro Sync settings in the cloud
Pro There's a free companion app for iOS that you can use to remote control your Mac
Pro Supports Apple script, bash, javascript
Pro Customize window button behaviour
Pro Make your own menu bar items
Pro Active community
Pro Built-in clipboard manager
Pro Highly configurable window moving / window snapping options
Pro Key sequences
Supports key sequences for things like text expansion.
Pro Supports MIDI devices (keyboards, DAW controllers, etc.)
Listen for MIDI events and have them control anything. For example you could use a DJ controller in your favorite video editor, etc.
Pro Lets you configure your external mouse's 4th and 5th button per app
Pro Record gestures / drawings and assign them to actions
Pro Developer is regularly adding features / improvements
Cons

Con A little slow
Similar to Spectacle, but it has a few more features, such as being able to pick the size adjustment increments. Spectacle was a little faster, though. Repeated size changes or moves in succession can cause it to wait for it to complete.

Con Imprecise when readjusting sizes
Con Doesn't support moving windows between workspaces
There's no way to move a window to a different workspace with hotkeys in ShiftIt.
