No ads, no forced "AI summary", doesn't sell my data to anyone. There are many other quality of life features, I don't consider any of them personally indispensable except for the ability to permanently remove a site from results, which I have used a few times.

I haven't used Google in many years so I can't directly compare the search quality, but Kagi is good enough that I've never had any reason to try something else since I've started using it.

Edit: I also use the !w Wikipedia bang constantly, I forgot that was a Kagi feature and not my browser. Obviously Kagi is not the only search engine with this feature though.