Flux, from Black Forest Labs, is the model developers reach for when realism matters and they want to build image generation into their own product. The quality, particularly on the things other models botch like hands and faces, is among the best available, and the open weights mean you can run smaller versions locally for free.
It is not a consumer app. You access Flux through hosted APIs (priced per image) or third-party tools that wrap it. For someone who just wants to type a prompt and get an image, Midjourney is friendlier. For an engineer adding image generation to an app at predictable per-image cost, Flux is the strongest option.