I've been using openjourney (and MJ/SD) quite a bit, and it does generate "better" with "less" compared to standard v1.5, but it's nowhere close to Midjourney v4.
Midjourney is so far ahead in generating "good" images across a wide space of styles and subjects using very little prompting. While SD requires careful negative prompts and extravagant prompting to generate something decent.
Very interested in being wrong about this, there's so much happening with SD that it's hard to keep up with what's working best.