Midjourney is the strongest fit for producing multiple polished graphic variants for social media ads and Instagram posts, as it excels at high-quality, stylistically consistent image generation and lets you iterate quickly with prompt variations to get different versions of a concept. You can run the same prompt with different style parameters or seeds to produce a batch of distinct but cohesive visuals ready for ad creative. Ideogram is worth considering if your graphics need accurate text overlaid on the image, since it handles typography far better than most image generators. DALL-E integrates directly with ChatGPT Plus, making it convenient if you want to combine copy writing and image generation in one workflow. Stable Diffusion is the best alternative if you want unlimited generations at no ongoing cost and are comfortable with a self-hosted setup.