I've used Midjourney and chatGPT. Midjourney is better for rapid iteration, cycling through options faster, and to a large extent getting "weirder". It's easier to tweak using parameters.

ChatGPT is far, far superior (especially now) when you want something more specific that you've already imagined. But it's slower, and unlike Midjourney you don't get four versions to choose to build and iterate on, you get a single image that takes longer to load.

    > four versions to choose to build and iterate on

How does this work? How do you ask a model to produce four different variations? Or do they have four different models run the same inference?

There's some noise in the process, so you won't get the same results if you ask the same model the same prompt 4 times. Most of the services that do this just ask the same model 4 times with a different random seed, as far as I can tell.

You don't ask to run four models, it's just that every single prompt you give it will return four models. You can then choose to have one of them iterated on, or upscaled.

If you're still not sure let me know and I'll show a screenshot.