Magit vs WinMerge

Simple tasks, such as commits, can quickly be made without leaving the editor.

Since it's integrated with Emacs, diffs are very easy to fix. You can jump right to any file you want to fix as soon as it comes up in the logs or in the status view.

You can easily learn the mnemonics for the most common tasks and use them to your advantage to speed up your workflow.

In Magit staging a hunk or even just part of a hunk is very easy.

Magit also implements several other "apply variants" in addition to staging and unstaging. For example: you can also discard or reverse a change, or apply it to the working tree.

brew install magit

You can quickly copy changed lines (or files in folder comparison) in both directions with keyboard shortcuts. You can edit the files as well, with syntax highlighting of some languages.

Can show what files has been changed in a folder, allows comparing files in tabs.

Can show differences within a line.

Winmerge is a free and open source tool.

Select two files and compare them. Alternatively, select one file, navigate elsewhere, select the other file to compare.
Also supports drag'n'drop of files / folders from Explorer.
History of past comparisons.

Binary is less than 3 MB, so it starts quickly

Can filter out files for folder comparison, lines for file comparisons, with regular expressions.
Options also allow to ignore whitespace differences, white lines, case change, line-ending changes, etc.

Keyboard shortcuts (and toolbar buttons) to navigate to next (previous) difference, side panel shows a map of the files with changed lines and allows to jump to a given place.

Detects when a block of lines has been moved in the file and shows the relation.