I think it depends a lot on the user. I never found DuckDuckGo to have good results, I think because it's based on Bing, and that remains laughable to this day (I have recently had to use it a bit and holy hell it's shit). I am comparing to startpage, which is I guess a more anonymous Google.
Kagi is at least as good for my day to day use, though I can't say it's obviously better. What it does have that I find useful is more ability to rank forum posts and the like higher, where they often have the real answers. Along with the "lenses" which let you kind of say what sort of stuff you're looking for - like only forum posts.
Right now, they also added to the Ultimate level a bunch of AI models you can chat with, which actually have pretty up to date knowledge it seems, and wider knowledge. For example, Claude 2 via Kagi was able to both help me as a DM with making a D&D 3.5e NPC (GPT4 can't do that alone, or at least didn't for me, and the plugin I tried to use that was suggested just didn't work at all), all the way to actually quickly finding JunOS commands and giving useful info about various outputs and clarifying what to do - which so far seem to be correct.
But the actual value to me is I can also ask GPT4 from Kagi, and Google Bison, so I don't need multiple subscriptions. I don't actually know how long this will hold true, but for now Kagi does a lot of stuff in one place that's pretty useful for me.