I'm a paying Kagi user. I don't think that I can give a clear example or explanation of why they are better, partly because it's been a long time since I used DDG, and I gave up pretty quickly. The one thing I can say is that, for the short time I was using DDG, I found myself doing a search, and then in most cases, immediately redoing the search using the !g, because the DDG results were bad, and even though I am also dissatisfied with google results these days, they were better. Kagi has the same functionality, but I find myself almost never using it.

That being said, if you personally are happy with your DDG results, then I'd say you should probably stick with it. Kagi _might_ be better for you than DDG, but if you aren't actively dissatisfied (the way I was with Google and everything else), then the room for improvement is smaller. Might be worth using their free tier (which is 100 queries per month I think) just to test out some side by side searches though.