FLUX.1 [dev] (non-commercial, weights-available): https://huggingface.co/black-forest-labs/FLUX.1-dev (Mindtown has a commercial license so all the images generated through it can be used for whatever purpose)
I am used to MidJourney already, so I wouldn't change to this service unless the prices a significant better.
While Flux isn't entirely open source due to the license (on some of their weights), it's a lot better ecosystem to build upon than fully closed Midjourney.
You're going to see AnimateDiff and Comfy and other things adapt to Flux, but you'll never see that for Midjourney.
I'd pick Flux just to enable more tooling and community use cases.