When comparing Emacs Org-mode vs TimeCamp, the Slant community recommends TimeCamp for most people. In the question“What are the best time tracking apps for freelancers?” TimeCamp is ranked 4th while Emacs Org-mode is ranked 7th. The most important reason people chose TimeCamp is:
Graphical timesheets placed in the calendar allows for an easy visual representation of how much time was used on what tasks on what hours for what days.
Specs
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Pros

Pro Ultimate flexibility
This app's flexibility is based on its minimalist approach, giving the user near-infinite freedom.
Pro Absolutely free
Emacs with Org-mode is free as in beer and free as in speech – that is, it costs nothing and it’s totally open source.

Pro Files are usable anywhere at anytime
Users are not tied to one service provider, program, platform, or database engine.

Pro Incredibly extensible
There are many plug-ins for Org-mode, including Org-habits and Org-notify. If Org-mode lacks some piece of functionality, it is very easy to add it.
Pro Agenda views
Pro Excellent unofficial Android app (orgzly)

Pro Offline support
Pro Efficient features for deadline organization
Pro Supports plaintext spreadsheets
Pro There are a lot of extensions, for exporting to html, bootstrap, js-reveal and much more
Pro Quickly add rich text
Pro Graphical timesheets
Graphical timesheets placed in the calendar allows for an easy visual representation of how much time was used on what tasks on what hours for what days.
Pro Available for mobile
Users can track time regardless of their time and location.
Pro Easiest of time tracking packages
Pro Great for teams
This software tracks your activity on PC. You can use timesheets, invite other members to your team, even freelancers.
Pro Can help create an invoice
TimeCamp can create an invoice based on your project hours. The app will take care of the math for you, you just need to provide it with the rate and tax. TimeCamp can also export directly to Xero or Quickbooks.
Pro Easily check team attendance
At a glance, the team leader can see how much his team has logged in as well as how much time they have taken off.
Pro Collaboration
Keeps the team up-to-date with their assignments, delivers the highest level of conversations.
Pro Automatic time tracking
Based on keywords users can configure the software to categorize time automatically.
Pro Billing
Pro Distractions-free design
Easy to use, even for a person who doesn't know anything about PM.

Pro Subtasts
You can easily define subtasks!

Pro Mobile app for iOS and Android
Pro Integrations
Integration with Trello allows to track time directly there.
Pro Task management feature
You can easily create and delegate task for your team.
Cons
Con Unintuitive user interface
The key combinations are unintuitive and difficult to remember. This is probably because there are a lot of hidden "modes" depending on where the cursor is. Actions aren't paired with reversing actions like in other todo apps. For example, hitting shift-tab does NOT reverse the effect of hitting tab.


Con Android app isn't very good
There are several user-created apps for Android, but none seem to offer the same level of functionality as other to-do apps.
Con Not really cross platform
Although it is possible to get a lot of it working, no all in one, sync included, out of the box solution is available for mobile devices.
Con By default, a hard-to-read display
The default way of writing an outline or checklist creates a very messy wall of text that's difficult to read with no vertical spacing. You can manually add vertical spacing, but the Org operations don't preserve it. There are pretty-display modes, but you need to remember how to enable them, etc. etc.
Con Free Version modified rendering everyone's tracked data useless
A recent change has made the Free Tier completely useless, locking off every single page in the computer time menu to the paid plan, which is simply unacceptable imo.
Con Can be intrusive
Due to the nature of the app and that it tracks everything a users does it can easily pick up on an employees website usage. Ideally one should not be cruising the web while working but realistically this can be seen as pretty overbearing of an employer.
Con Numbers may be off
Instances of incorrect times for certain activities is pretty damning of an app that is supposed to track time accurately.
Con Free Version modified rendering everyone's tracked data useless
A recent change has made the Free Tier completely useless, locking off every single page in the computer time menu to the paid plan, which is simply unacceptable imo.
Con No clients
You can't define clients and assign projects.
