Nano Banana 2.1 vs GPT Image 2.5 vs Seedream 5.0: one prompt, first try, four tests

Three of the most talked-about image models shipped new versions this autumn: Google's Nano Banana 2.1, OpenAI's GPT Image 2.5 and ByteDance's Seedream 5.0. Most comparisons use English prompts and pick the best of several tries. I wanted something closer to everyday use, so I ran the same prompt once on each model and kept the first result, including two prompts that ask for Chinese text inside the image, which is where models still slip.

Setup

• Same prompt for all three, portrait 3:4, 1K resolution, one generation each, no retries, no editing.
• All three run with the same parameters on one platform, so default settings do not differ between sites.
• Price per image at these settings: Nano Banana 2.1 about $0.048, GPT Image 2.5 (Sunburst, high quality) about $0.031, Seedream 5.0 Pro about $0.036.

In every comparison image, left to right: Nano Banana 2.1 | GPT Image 2.5 | Seedream 5.0.

Test 1: a poster with exact Chinese text

Prompt (translated): a portrait grand-opening poster for a bubble tea shop, warm illustration style, big title "开业大吉" (Grand Opening), a line "全场第二杯半价" (second cup half price) and a small footer "11月8日 · 人民路88号" (Nov 8 · 88 Renmin Road), clean layout, no typos.

• Nano Banana 2.1 produced a lovely poster but translated every line into English. It ignored the instruction.
• GPT Image 2.5 rendered all three Chinese lines correctly and the layout looks like a real commercial poster.
• Seedream 5.0 also got every character right, in a softer, cuter style, and invented a "Dear Tea" cup design.

Test 2: a hand-drawn infographic with Chinese labels

Prompt (translated): a hand-drawn infographic titled "手冲咖啡四步法" (four steps to pour-over coffee), four steps left to right with sketches: grind (medium-fine), wet the filter, bloom 30 seconds, pour in stages, a short Chinese caption under each, beige paper background.

• Nano Banana 2.1 went bilingual with English first, in a 2×2 grid instead of left to right.
• GPT Image 2.5 gave the cleanest result: four numbered steps in a row, correct and readable Chinese captions.
• Seedream 5.0 has the strongest hand-drawn feel with correct titles and steps; one small caption has a redundant annotation.

Test 3: an e-commerce product shot

Prompt: an amber glass perfume bottle on wet dark slate after rain, a few damp green leaves, soft side light, shallow depth of field, premium commercial photography.

All three are usable. Nano Banana 2.1 looks the most like a real photo (and made up a label). GPT Image 2.5 looks the most "luxury ad". Seedream 5.0 is clean and minimal. For your own product, use image-to-image with a real photo instead of asking a model to invent the bottle.

Test 4: imagination

Prompt: a corgi in a white spacesuit sitting on the Moon eating Sichuan hot pot, red chili broth steaming, blue Earth in the distance, cinematic light.

• Nano Banana 2.1: good composition, but the corgi is small and took its helmet off on the Moon.
• GPT Image 2.5: the most striking close-up, though it drew a NASA logo on the suit, which matters if you use it commercially.
• Seedream 5.0: helmet on, the richest details, and the best grasp of "Sichuan hot pot".

Takeaways

• Posters, cards and diagrams with exact text, especially non-English: start with GPT Image 2.5, then Seedream 5.0.
• Photoreal products and portraits: Nano Banana 2.1 is still excellent; just don't rely on it for Chinese text.
• Scenes with Chinese cultural context: Seedream 5.0 understood them best.

No model won everything. At two or three cents an image, running one prompt on all three and picking the best is faster than rewriting the prompt again and again. I ran these on PopNow, where the three models sit behind one account and the price shows before each run.

All images are first generations with no edits, and the prompts are above if you want to reproduce them.

Disclosure: I work on PopNow.