When comparing Xfce Whisker Menu vs Synapse, the Slant community recommends Xfce Whisker Menu for most people. In the question“What are the best app launchers for UNIX-like systems?” Xfce Whisker Menu is ranked 6th while Synapse is ranked 9th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro The most simple and convenient app launcher on my experience
Pro Built into Xfce desktop environment
Pro Rock solid
Synapse is pretty rock solid. Works as expected and launches applications fast.
Pro Can run commands just as a terminal would
Users can run commands such as sudo apt-get update
from within Synapse, making for a convenient way to open or run items/commands.
Pro Zeitgeist powered
Synapse searches the Zeitgeist log, which tends to be a pretty quick way to do searches over other app launchers.
Pro Includes a Zeal plugin
Includes a Zeal plugin to make searching faster.
Cons
Con Will not support file search
Limited to application launch: https://bugzilla.xfce.org/show_bug.cgi?id=11551#c2
Con Synapse is an abandoned project
The latest release was 7 years ago and the Launchpad page is a ghost town
Con Unable to search whole system
Due to Zeitgeist being used the search is not as robust as if it were using Tracker. Of course using Tracker has its own downside like battery drain, so currently there is no "best" solution.
Con Bound to control+space
Due to this it interferes with common IDE layouts for recommendations. Modifying hotkeys file doesn't adjust this.