What's the core difference?
DALL·E is tuned to follow descriptive natural language closely. Longer, well-structured sentences that specify the subject, setting, mood, and details tend to produce more faithful results. It does not use a parameter-flag syntax the way Midjourney does; you control the image through the words themselves.
Midjourney is tuned for terse, comma-separated keyword phrases — subject, medium, style, lighting, composition — followed by parameters that adjust aspect ratio, stylization, variation, and more. The flags do work that you would otherwise express in prose. For the full structure, see our Midjourney prompt formula breakdown, and the parameter reference in the Midjourney docs.
In short: DALL·E listens to sentences; Midjourney listens to keywords plus dials.