So I did a catalyst build of EX a while back (which is where https://github.com/rust-lang/rust/issues/106021 came from) - but rather anticlimactically the end result looked almost identical to the normal iOS app when running under macOS; I don't remember the sidebar/toolbar looking particularly better, and that was my main reason for doing the build in the first place (to get a flexibly resizable left toolbar). The main advantage seemed to be that it would run on Intel.

If things have improved I'd love to know, and then perhaps we'll have another shot at it. Are there any good comparison screenshots of the two approaches (with a toy app, i guess) anywhere?

I think the benefit is more that you get access to AppKit APIs. This lets you integrate with the OS the way users expect.

For example wrt scaling, Apple’s Mac Catalyst guide says:

> When you first create your Mac app using Mac Catalyst, Xcode defaults to the “Scale Interface to Match iPad” setting, or iPad idiom. With this setting, the system ensures that your Mac app appears consistent with the macOS display environment without requiring significant changes to the app’s layout. However, text and graphics may appear slightly less detailed because iPadOS views and text scale down to 77% in macOS when you use the iPad idiom. For example, the system scales text that uses the iPadOS baseline font size of 17pt down to 13pt in macOS.

So you gotta change that setting, and then use whatever SwiftUI components (or straight up AppKit APIs) allow for that native look :)