I think Kagi at this stage have a better reputation than Mozilla, and Chromium is not seen as sufficiently independent from Chrome, and hence from Google’s anti-user decisions.

That said, closed source is still a deal breaker for a browser for me, or I’d probably already be using Vivaldi.

The built in ad blocker is phenomenal. Only Brave is as good on this front. It supports extensions from both FF and Chromium. It has a really neat integration with Kagi private search in private tabs. Kagi as a company has generally pretty good ethics and respects their users. That’s enough to make it compelling for me.

FF and Chromium are controlled by the biggest advertising company on the internet, while Orion is developed by a privacy focused search engine.

Don't worry about it, you're not even invited to use Orion.

Nothing, really, other than it being closed-source, based around Webkit and to be sold/distributed under the Kagi moniker. If that combination scratches your itch this is for you, otherwise there are many alternatives.