The stable version of Toggl on Linux installs as a Chrome app thus Chrome has to be installed on the machine and run (it can be run as a process in the background). A native client is in the works, but it's still in beta.
An overview of all tracked activity over a day, a week, or a month is available that helps get an understanding of how activity is distributed over time. The overview can also be exported to an HTML file that's intended for printing.
Everything in TMetric is simplified for user convenience. You can easily track how much money you earned working with your clients. This feature gives you a perfect overview what clients give you the most income.
See which apps are used and which websites were visited the most while tracking time. You can also see how active you are while you track time by measuring keystrokes and mouse movements (keystrokes are not recorded) and color coded in your activity view so you can see how productive you are.
Many other time tracking apps allow for free users under a certain team size and for personal use, Hubstaff does not allow for this and only has a limited 14 day trial of the software before one needs to pay a monthly fee that starts at $5 a month for the lowest package.