I'm not sure it matters anymore unfortunately. I've vibe coded a few apps using gpui-kit and it works well. It helps that gpui-kit provides a number of high quality components (e.g. the data table is especially good). But even where it doesn't (e.g. log output) Opus 5.5 was able to easily write one that worked perfectly.

It even added ANSI colour support... which I am still on the fence about but it did make the very good point that it means the logging is exactly the same in GUI and CLI mode.