I'm genuinely curious - I heard of lot of BC being 'the tool' for diffing. I'm used to Meld, but my current employee has a pretty strict policy which tools could be used so at some point I've managed a licence for some older version of BC. But for some reason I've found its UI/the way it works a bit less optimal that I was accustomed for. Since I'm using that primarily for text diffs these day I usually use a diff tool from IntelliJ Idea (I have Idea open all the time).
For me, I eliminated BC immediately because I was often diffing prose and it didn't have word wrap; that ability is apparently available now in the beta version of BC5, but it wasn't when I was testing it. I suspect it will continue to be non-optimized for prose in how it handles long lines.