Nano Banana vs ChatGPT 4o: Which AI Generator is Better?

Recently, Google has unveiled a new model called Gemini 2.5 Flash Image, aka Nano Banana, and it is a lot of fun to use. It is quick, executes the requirements of the editing tasks effortlessly, and the image generation of Nano banana is seamless yet also creative. 

Of course, we have ChatGPT 4o image generator, which is also a pretty functional experience for image generation and edits, so I decided to run both models side by side on the same prompts and see which one would generate better results. That’s what this comparison is all about: Nano Banana vs ChatGPT 4o for image editing and generation.  Let's take a look.

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Test 1. Generate a baby photo from two parent pictures

💡Prompt: Generate a realistic baby photo from two parent pictures.

Results: While creating a baby photo using two parental images, I noticed that ChatGPT 4o output a photo of the baby, and it reflected the father's skin tone a bit better. Since the father had a remainder of darker skin tone, and ChatGPT accurately visualized this, It felt more realistic and accurate overall.

Test 2. Outfit and background swaps

💡Prompt: Transform the woman’s outfit into a chic, modern streetwear style with a denim jacket, cargo pants, and sneakers. Change the background to a vibrant Tokyo Shibuya street at night, filled with neon lights and bustling crowds.

Results: Nano Banana performed better at keeping the facial features similar, which made the results look closer to the original person. With Chat GPT 4o, the face was slightly different with the original person, and lost some resemblance.

Test 3: AI-generated product shots

💡Prompt: Place the perfume bottle ok a glossy black marble surface with subtle reflections, soft spotlighting, and a blurred backdrop of shimmering golden bokeh lights.

Results: Both AI-generated product shots provided good results. Nano Banana was very close to the prompt and captured the details quite well. ChatGPT 4o captured more of the overall feel, and the golden lights in this rendering were larger and blurrier and still looked fantastic. Overall, both had excellent results with different styles.

Test 4: Facial Expression Control

💡Prompt: Keep the person in the image unchanged, but adjust the facial expression to look angry. Preserve the pose, body shape, hairstyle, and overall appearance while maintaining realistic lighting, shadows, and photorealistic detail.

Results: Nano Banana's outcome appeared more confused than angry, whereas ChatGPT 4o actually presented an angry expression, and yet Nano Banana did keep the person’s face quite close to the original, enabling strong consistency. ChatGPT 4o had the better facial expression, but some of the facial features were somewhat off, but the individual’s facial features were still recognizable.

Test 5: Change the posture of your subjects

💡Prompt: Change the photo so that the man is carrying the woman in a princess carry pose.

Results: Both models successfully switched the pose to a princess carry. Nano Banana was able to demonstrate strong consistency in the characters’ facial features and posture, while ChatGPT 4o result displayed a somewhat less accurate face, but was still distinguishable.

Test 6: Add Object to Image

💡Prompt: Add a fried egg and a sausage on top of the noodles. Place them naturally, while keeping all the original elements of the dish unchanged.

Results: Both models did well adding a fried egg and sausage on top of the noodles, which turned out nicely. Nano Banana added extra detail by having the sausage shown with two knife cuts, and ChatGPT 4o used a touch of spicy powder from the original photo. Both models served well and adding unique details.

Test 7: Extract Object

💡Prompt: Extract the clothing from Image and create a clean e-commerce product photo. Remove the model entirely and showcase the garment with professional lighting and a clear background.

Results: Both models captured the clothing and generated a polished e-commerce product photo. The key difference lies in the lighting and color tone: Nano Banana's result was more accurately representing the original color of the garment while the ChatGPT 4o output provided a slightly different color tint.

Test 8: Merge and combine images into one

💡Prompt: Merge all the photos into a scene of a cat lying on a swimming ring in a swimming pool. The cat is wearing sunglasses, and a hand is holding two pieces of watermelon.

Results: Both models successfully embodied the prompt by composing all the photo elements, resulting in a fun and playful scene. They look great as results and convey the concept of the prompt well.

Final thoughts

Both Nano Banana and ChatGPT 4o have their advantages, and it's hard to say that one model is better than the other for every activity. ChatGPT 4o sometimes provides more accurate or realistic outcomes, like natural skin tones during baby generation or better facial expressions. However, Nano Banana consistently outputs characters while keeping the facial features intact. Ultimately, the best model will depend on your prompt, and what you want to achieve with the activity, and seeing the models operate on the same prompt will help you know which AI filters fits your needs. Using both is the best option to see the differences in output in order to learn which model works best for your specific activity type.