I used kdiff3 and could never understand people complaining so much about SVN merges. Now I use kdiff3 in Git and it's fine, too. What isn't fine (though occasionally improving) is Git's UI and mess of termnology and concepts.
It's been a long time since I used it, I don't remember what I was using for diffs, but I suspect it was just whatever the default built in diff support was.
It occurs to me that many people these days use git with github exclusively, and have it configured to only allow commits via PR, and only allow either squash or rebase merges, it's kinda SVN with extra steps.
