Base UI is more low-level, a lot less opinionated and doesn’t force you into certain layouts. This of course makes it more complex to use, but that doesn’t matter if you’re using shadcn components because they’re doing that work for you.

So essentially they look and operate the same as Radix components at the shadcn level but you have low-level control later on should you need it.

I tried to use baseUI and gave up. Forms are a bit different and I can't no longer copy/paste similar form code between projects (unless I migrate everything to baseUI).