Recs.
Updated
SpecsUpdate
Pros
Pro Resolves many git merge conflicts without requiring any user action
Beyond Compare does a better job at resolving merge conflicts than git itself - you can review everything. In daily practice, it turns out many git conflicts are super easy to resolve (or already resolved on load) by Beyond Compare, particularly when you're working on repositories where some people tend to rebase rather than merge. This saves you a lot of time when you want to sync with such rebased branches/mainline.
It is also very helpful that conflicting diffs (next to diffs from baseline) are marked up as such and diffs can be toggled as 'conflicts' (red exclamation mark in left-side visual diff-zones overview-strip in BC: on/off)
Pro User friendly view of changes on a single line
When comparing changes in merge conflicts, the fourth panel shows all versions of the same line.
Changes are marked up on a character-by-character base instead of only line-based so that you can quickly spot which bit (or bits!) have changed in each line of code that's part of the conflict/change.
Pro Easy visible color coding of whitespace-only vs. real/important edits for faster change inspection and decision making
This is very useful in both 'git merge' activity and regular 'git commit' diff inspection (the combo of Beyond Compare and TortoiseGit results in a superb UX) to quickly inspect and decide on merge conflicts and applied changes/edits.
'Whitespace' isn't set in stone: you can configure Beyond Compare so that it can recognize various things as 'unimportant whitespace-like changes', e.g. leading spaces, trailing spaces, but also comments, etc.
Pro Fast keyboard shortcuts to jump between merge conflicts and to resolve them
Has different keyboard shortcuts to jump between (both up & down) merge conflicts and basic change edits (non-conflicting); together with 'take left side, take right side, take left, then right', etc. keyboard shortcuts, the git merge resolve process is 100% keyboard driven and faster than when you must move the mouse and/or swap between keyboard and mouse.
The different shortcuts for conflict navigation vs. change navigation makes it very easy to go through a change set and see if you ultimately agree or disagree with the edits.
Pro The 'merge result' is freely editable from within the diff tool: any 'post-fact' editing you wish to do can be done without starting your editor
Often when you resolve conflicting merges, you'll find that you want/need to fiddle with the result a bit, do some hand tweaking in there.
Beyond Compare is also a full text editor, allowing you to apply such 'post fact' manual edits within the diff tool, resulting in a fast and powerful merge conflict resolution process.
Pro Has rules for adding ignore-masks and replacement rules
So parts you don't want to see in your comparision can be hidden with ignore masks. Parts that are okay to be changed can be set with change-lists so beyond compare knows what's the replacement value and skips displaying this. So you can focus on the for you important changes. For example with the ignore mask I was able to compare two logs with different timestamps but nearly same content. (beginning with timestams the first x characters adding to ignore)
Cons
Con Proprietary software
Beyond Compare is not free, it offers different license options depending on the number of members in a team and depending on the software version.