A lot of features for free,stable behaviour, nice customisable interface.
Great tool for Diffs
Donovan J. Edye
Latest version is https://sourceforge.net/projects/winmerge/files/1.%20Stable%20versions/2.12.4/WinMerge-2.12.4-Setup.exe/download
Does what you expect.
File Compression and File Comparison are different things. Althought there is no best match, I would appreciate to have this this program in a more proper category like Development - Source Editors, System Utilities - Text/Document Editors, System Utilities - Other, etc.