It depends. In terms of accuracy, I've seen new streets missing in OSM that are updated in Google Maps, but also the other way around.
If you want to find korean restaurants or cheap hairdressers, Google Maps unfortunately still has an edge over OSM. If you want to find hiking trails, it's the other way around.
OSM is missing things like satellite images and Street View, which is undeniably useful sometimes.
I wouldn't say it's worse, but it's better only for certain use cases, and worse for others. :)
It's not the best, and quite clearly not a priority of the project yet. I'd say map integration is a little bit worse than in DuckDuckGo, which is already not as good as Google. If this is important to you it's probably too early to jump on Kagi.
On the positive side I didn't realize this before just now when checking it out in order to answer your question, so it hasn't bothered me much. Usually when I need address information I go straight to the service I see best fit.
I'd love to see Kagi make an effort to push OSM though, but that's probably not exactly on top of their priorities.
Unfortunately, it often means going straight to maps.google.com or the Google Maps app - it's the main Google service I still haven't gotten rid off in my life. If I need something a bit more simple I'll check Open Street Maps, either through a desktop app or Organic Maps on my phone. If I need hiking trails Organic Maps is clearly superior to Google Maps, so then there's no real question.