Recs.
Updated
SpecsUpdate
Pros
Pro Easy to understand and use
In a nutshell Meld shows the difference between the same file at different points in git branches by highlighting the text differences and with arrows. Simply by clicking on an arrow next to highlighted text that you want all version of the file to have, makes sure that there is a continuity of text in the same file at different positions in git branches- i.e it removes any conflict.
Pro Easy to use and visually appealing
Stragihtforward and you don't need to read tutorials to use it. Just click and select and you instantly see how the difference and merges are connected to eachother.
3 sub- windows, instead of 4, which reduces the mess during merge and let you see more of the surrounding files rather than just 5 lines.
Pro Cross platform
Supports many different OSes including Windows, Linux, and macOS.
Pro Supports some simple version control actions
Meld supports the major version control systems (Git, Mercurial, Subversion and Bazaar). You can launch file comparisons between different versions to see what parts changed before commiting.
Simple version control actions are also supported and possible. For example: commit/update/add/remove/delete files.
Pro Internationalization
Through the GNOME Translation project and the translators that have worked for it, Meld is available in multiple languages. You can check if your language is supported in the translation statistics page.
If you can't find your language or if your language translation is unfinished and you want to help, you can do so by joining the GNOME Translation Project.
Cons
Con Lacks a result view
When comparing two files you can only move changes from one pane to the other, and save the file in each pane. There's no way to actually merge the files into a result file using lines from each of the diffed files.
Con Slow start-up on Windows
Update: This issue should be fixed on Meld-3.18.1-win32.msi released on 27 May 2018. See http://meldmerge.org/news.html
Recommendations
Comments
Flagged Pros + Cons
Pro Supports editing files directly
In addition to comparing two files it also allows you to edit them right in place. What's more, the diffs are updated automatically.