Short answer
For high-consistency product lifestyle shots + fast iteration for ad testing, lean toward Leonardo AI as your primary pipeline and use Midjourney for occasional highly stylized hero variants. Leonardo generally gives faster, more repeatable batch workflows and built-in tools for image-based consistency; Midjourney wins on purely artistic, dramatic visuals but is harder to lock down for pixel‑level repeatability.

Why (practical comparison)
- Consistency & templates: Leonardo is built around canvases/templates, image-to-image and inpainting workflows that make it easier to paste a single product asset into many scenes with consistent lighting and placement. Midjourney can be forced toward consistency (seeds, same prompt skeleton), but you’ll spend more manual time curating variations.
- Batch generation & iteration speed: Leonardo typically supports multi‑image batching and quicker in-browser iterations; this reduces hands-on tweaking when you need 20–100 ad variants. Midjourney’s grid + variations model works, but parallel throughput and exact reproducibility are more limited unless you use more manual orchestration.
- Prompt control: Midjourney offers granular creative control (stylize, aspect, chaos, version flags) that artists love. Leonardo’s prompt controls are strong for realistic/photo workflows and often easier to combine with image-based edits (masks). For product ads, Leonardo’s image-guided controls are usually more practical.
- Output quality: Both can produce high-quality images. If you need hyper-photorealism and exact product detail, prioritize a workflow using product photos + inpainting (Leonardo or specialised photoreal models). For stylized brand looks, Midjourney can outshine in one-off hero images.

Recommendation
Primary: Use Leonardo AI for batch lifestyle shots and ad testing pipeline. Secondary: Use Midjourney for creative hero images and brand-driven experiments.

Decision criteria (use these to choose)
- Need near-identical product placement across variants → Leonardo
- Need fast batches of 10–100 ads → Leonardo
- Need highly artistic/stylized hero creatives → Midjourney
- Limited budget/one-person team → choose the tool you can set up fastest (Leonardo often quicker for template-based workflows)
- Want maximum prompt-art control and unique looks → Midjourney

Practical checklist to implement now
1. Prepare assets: high-res product PNG (transparent), 3–5 reference lifestyle photos (lighting/camera angle). 2. Build a prompt skeleton: fixed camera, lighting, product placement, mood, callouts; leave slots for variant text (color, background). 3. Create 3–5 scene templates (mood + composition). 4. Use image-to-image + masked inpainting to paste product into templates (lock product size/position). 5. Batch-generate 20 variants per template; export at platform sizes. 6. Run quick QA: product visibility, correct color, brand-safe. 7. Iterate with A/B results: tweak only one variable at a time (lighting, model presence, copy).

Best-for / Avoid-if
- Best for Leonardo: fast, repeatable e‑commerce shots, templated batch generation. Avoid if you need highly stylized, painterly art.
- Best for Midjourney: standout hero creatives and explorations. Avoid if you need identical product placement across dozens of images.

Note on constraints
The right choice depends on budget, team prompt‑engineering skill, and whether you’re at early creative exploration or scaling hundreds of variants. If you want, I can sketch a prompt skeleton + masking steps tailored to one of your product photos.

Compare Midjourney and Leonardo AI