Nice to see OpenAI catching up to Midjourney. It's been interesting to see how good Midjourney is compared to DALL-E and StableDiffusion. There has been a wide gap in quality for awhile now.
I think it’s more subjective than that. For me the Stable Diffusion experience is far ahead of Midjourney. Running it locally, hundreds of custom models online for any kind of image you want, controlnet, plus it’s free.
The open source community is pushing forward SD forward far faster than Midjourney is improving.
Not yet, but from the news I've heard of Version 6, that is the plan. They're working on a big website update and at first they will allow the use of both, and over time I think the plan is to build new features for the website UI only. That's because they're running into major limitations with Discord when it comes to more advanced stuff like region painting and so on.