In terms of release cadence: before the 3.5.x series, KMate for Mac was updated faster than the Windows version, while Windows followed a branch-based release model.
Starting from version 3.5.33, the Mac and Windows editions moved to synchronized dual-platform releases, so the latest features and fixes now apply to both platforms at the same time. However, because Mac App Store and Microsoft Store reviews follow different processes, listing availability may still differ slightly.
In terms of functionality: the core feature set is fully aligned across both platforms, including highlight and note management, dictionary management, and Reading Mode. Because macOS sandbox permissions are stricter than Windows, the Mac version requires a one-time authorization when you first connect a classic Kindle or add dictionary files. The Windows version also supports automatic Kindle model and connection status detection.