Recs.
Updated
SpecsUpdate
Pros
Pro Comparing two or more different folders is supported
Meld allows users to compare two or three different folders for differences. But if a user wants to 'zoom in' and compare files contained in these folders, Meld gives you the ability to do so and launch file comparisons between files contained in different folders or in the same folder.
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 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 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 Program opens slow 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
Con No official OSX Support
Some attempts have been made to port, but nothing easy or fully working.
Recommendations
Comments
Out of Date Pros + Cons
Con Python 3 not supported
May or may not be an issue, but if you are trying to standardize on Python 3 for all new projects, having to keep 2.7 around just to support a merge tool might not be ideal.