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Pro Comes already integrated with the one of the best Linux desktop environments
It's a part of Plasma 5 which is one of the best Linux desktop environments currently, so it has complete integration and is already included with the basic packages.
Pro Can be configured to work as you like
Length of the history, persistence between sessions, what to do with trailing white spaces, basically whatever you could wish to change is configurable.
Pro Pre-configured button to create a QR code out of any clips
If you're not already using KDE Connect to exchange clipboard entries with your mobile devices, this one is a lifesaver. It's also handy when someone else needs to copy one of your clips.
Con Since it's part of Plasma it might not be the best choice for other DEs/WMs
No complete integration, will pull in a lot of Plasma dependencies....