Short answer: pick GPT Image 2 when you want the lower price per image, many references (up to 16) or extra-wide and extra-tall frames such as 2:1 and 1:2. Pick Nano Banana Pro when you need 4:5 or 5:4 portrait and print frames, and one call that handles both prompts and edits. On AgentReel a 2K image costs 3 credits on GPT Image 2 and 5 credits on Nano Banana Pro.
This Nano Banana Pro vs GPT Image 2 comparison uses two sources: the parameters in the Kie API documentation and the prices AgentReel charges today. Both models run through the Kie.ai API, and both sit behind the same prompt box in AgentReel. We do not quote a benchmark score, because no neutral benchmark covers both models with the same prompts.
Nano Banana Pro vs GPT Image 2 at a glance
| Nano Banana Pro (Google) | GPT Image 2 (OpenAI) | |
|---|---|---|
| Endpoints in the API | One, with optional image input | Two: text-to-image and image-to-image |
| Reference images in the API | Up to 8 (JPEG, PNG, WebP, 30 MB each) | Up to 16 |
| Prompt length | Up to 20,000 characters | Up to 20,000 characters |
| Resolution | 1K, 2K, 4K | 1K, 2K, 4K |
| Aspect ratios in the API | 11, including auto, 4:5, 5:4 and 21:9 | 16, including auto, 2:1, 1:2, 3:1, 1:3 and 9:21 |
| Ratio limits by resolution | None listed | 2K drops 5:4, 4:5, 3:1, 1:3, 9:21; 4K drops 3:1, 1:3, 9:21 |
| Transparent background in the API | Not listed | Yes, at 1K only |
| Output format in the API | PNG or JPG | Not listed |
| AgentReel price, 1K / 2K / 4K | 5 / 5 / 6 credits | 2 / 3 / 4 credits |
Prices are AgentReel credits on October 20, 2026. The Generate button always shows the current price before a job starts. See pricing for credit packs.
What the Kie API supports and what AgentReel exposes
The API and the AgentReel form are not the same thing. Here is where they differ:
- Nano Banana Pro: AgentReel offers all 11 aspect ratios, up to 8 references and all three resolutions. It always asks for PNG output.
- GPT Image 2: AgentReel offers up to 16 references and all three resolutions. It shows 11 of the 16 aspect ratios: auto, 1:1, 3:2, 2:3, 4:3, 3:4, 16:9, 9:16, 2:1, 1:2 and 21:9. The 5:4, 4:5, 3:1, 1:3 and 9:21 ratios stay API-only.
- Transparent background: the Kie API offers a background parameter for GPT Image 2. AgentReel does not send it today, so you cannot ask for a transparent PNG from the AgentReel form.
- Endpoint choice: GPT Image 2 has separate text-to-image and image-to-image endpoints. AgentReel picks the right one for you. It uses image-to-image as soon as you attach a reference.
What Nano Banana Pro does best
Example output from Kie's Nano Banana Pro page.
One call for prompts and edits
Nano Banana Pro takes a prompt and an optional list of input images in the same request. The Kie docs describe these images as pictures "to transform or use as reference". So the same model covers a fresh image, a restyle and a composite of several photos. You do not switch modes. Each input can be JPEG, PNG or WebP, up to 30 MB.
Portrait and print frames
Nano Banana Pro offers 4:5 and 5:4, and the API lists no resolution limit for any ratio. That matters for feed posts and print layouts at 4K. In AgentReel, GPT Image 2 has no 4:5 or 5:4 option at all. In the API, GPT Image 2 offers those two ratios at 1K and 4K, but not at 2K.
Where it costs more
Nano Banana Pro costs 5 credits at 1K and 2K, and 6 credits at 4K. Because 1K and 2K cost the same, render at 2K unless you need the extra detail of 4K. Ten 2K images cost 50 credits, against 30 on GPT Image 2.
What GPT Image 2 does best
Example output from Kie's GPT Image 2 page.
Many references in one image
GPT Image 2 accepts up to 16 input images in its image-to-image endpoint, twice the limit of Nano Banana Pro. Use it when one image must pull from many sources: a product from several angles, a logo, a color palette and a scene. Say in the prompt what each image is for.
Wide and tall frames
The API lists 16 aspect ratios for GPT Image 2. AgentReel offers 2:1 and 1:2 among them, which Nano Banana Pro does not have. A 2:1 frame suits a web banner. A 1:2 frame suits a tall story graphic or a phone wallpaper. The API also offers 3:1, 1:3 and 9:21, but only at 1K.
Transparent backgrounds through the API
The background parameter takes transparent, opaque or auto. It works only at 1K. If you call Kie directly, you can request a cut-out sticker or a product on a clear background. On AgentReel this option is not exposed, as noted above.
Lower price at every resolution
On AgentReel GPT Image 2 costs 2 credits at 1K, 3 at 2K and 4 at 4K. That is the cheaper choice at all three sizes. It makes GPT Image 2 a good model to draft many ideas before you settle on one.
Price per image on AgentReel
| Batch | Nano Banana Pro | GPT Image 2 |
|---|---|---|
| 1 image at 1K | 5 | 2 |
| 1 image at 2K | 5 | 3 |
| 1 image at 4K | 6 | 4 |
| 10 images at 2K | 50 | 30 |
| 5 carousel slides at 2K | 25 | 15 |
References do not change the price on either model. You pay by resolution only.
Which one should you choose?
- Many drafts on a budget: GPT Image 2 at 1K.
- An image built from more than 8 references: GPT Image 2.
- A 2:1 banner or a 1:2 story graphic: GPT Image 2.
- A 4:5 feed post or a 5:4 print frame: Nano Banana Pro.
- A 4K image in any ratio the model lists: Nano Banana Pro, whose docs list no ratio limits by resolution.
- A transparent PNG: GPT Image 2 through the Kie API at 1K. AgentReel does not offer it yet.
- Edit or restyle one photo: both work. Start on GPT Image 2 for cost, and switch if the result is not right.
For a multi-slide post, use the TikTok carousel maker. It writes the copy and creates a photo for every slide. To compare other image models, read Seedream 5.0 Pro vs Flux 2 Pro. For video, read Seedance 2.0 vs Kling 3.0.
FAQ
Is Nano Banana Pro better than GPT Image 2?
Neither is better for every job. GPT Image 2 is cheaper, takes more references and offers wider and taller frames. Nano Banana Pro offers 4:5 and 5:4 and its docs list no ratio limits at 2K or 4K.
Which model is cheaper on AgentReel?
GPT Image 2. A 2K image costs 3 credits, against 5 credits on Nano Banana Pro. At 4K the prices are 4 and 6 credits.
Can either model make a transparent background?
GPT Image 2 can, through the Kie API, at 1K only. The Nano Banana Pro docs list no background option. AgentReel does not expose the transparent option for either model today.
How many reference images can I upload?
Up to 8 on Nano Banana Pro and up to 16 on GPT Image 2. AgentReel allows the same limits as the API.
Do these models cost credits for a free account?
Yes. Both models need credits from a purchase. A free AgentReel account can make one Z-Image image a day. See pricing for credit packs.
How we compared
We read the Kie.ai API reference for Nano Banana Pro and GPT Image 2 on October 20, 2026, together with the GPT Image 2 image-to-image page. Prices come from the AgentReel model catalog on the same day, which is the same table that charges your account. The images are example outputs from Kie's model pages.
