Understanding AI Image Models: Flux vs Stable Diffusion vs Nano Banana

Apefx offers 27+ AI models — but they’re not all the same technology wearing different hats. Different models use fundamentally different architectures, and understanding those differences helps you choose the right model for each task. This guide explains the three main approaches to AI image generation in plain language.

Why Architecture Matters

You don’t need to understand model architecture to use AI image generation. But knowing the basics helps you:

• Choose faster: Instead of trying all 27 models, you can narrow down based on what each architecture does best
• Write better prompts: Different architectures respond differently to prompt structures
• Predict behavior: Understanding why a model does something helps you work around its limitations
• Explain to clients: If you’re using AI commercially, understanding the technology builds credibility

Diffusion Models

Examples on Apefx: Flux Pro, Flux 2 Klein, Nano Banana 2, Nano Banana Pro, Seedream 5.0

How They Work

Diffusion models start with pure random noise and gradually remove it, step by step, guided by your text prompt. Imagine a sculptor starting with a block of marble and chipping away material in 20–50 passes, with your prompt acting as the blueprint.

The technical process:

1. Forward diffusion (training): The model learns by watching images get progressively noisier — clean image → slightly noisy → more noisy → pure noise
2. Reverse diffusion (generation): At generation time, the model runs this process backward — starting from noise and predicting what the “less noisy” version should look like at each step
3. Text conditioning: Your prompt is encoded into a mathematical representation that guides each denoising step, ensuring the emerging image matches your description

Strengths

• High quality: Diffusion models produce exceptionally detailed, high-fidelity images
• Prompt adherence: Strong connection between text and output — what you describe is what you get
• Style flexibility: Can generate photorealism, illustration, abstract art, and everything in between
• Well-understood: The most researched architecture with mature optimization techniques

Weaknesses

• Speed: Multiple denoising steps mean generation takes time. Each step is a full neural network pass
• Consistency: Small changes in the prompt or random seed can produce very different outputs
• Complex compositions: Can struggle with scenes containing many distinct objects or specific spatial relationships

Flux: The BFL Family

Flux models from BFL (Black Forest Labs) are among the most popular diffusion models. On Apefx:

• Flux 2 Klein (1 credit, instant): A distilled version that trades quality for extreme speed. Uses fewer denoising steps, producing good-enough results near-instantly. Perfect for iteration and previewing prompts
• Flux Pro (5 credits, fast): The full-quality Flux model. Consistent, reliable, and fast enough for production use. The workhorse of many professional workflows

Nano Banana: Google’s Gemini-Powered Models

Nano Banana models are powered by Google’s Gemini architecture, which combines diffusion with advanced language understanding:

• Nano Banana 2 (8 credits, fast): Based on Gemini 3.1 Flash. Excellent text rendering within images and fast generation. Great for images that need readable text (signs, labels, UI mockups)
• Nano Banana Pro (15 credits, medium): Based on Gemini 3 Pro. The highest quality model on the platform with native character consistency. The go-to for hero images and professional work

Autoregressive Models

Examples on Apefx: BitDance

How They Work

Autoregressive models generate images piece by piece, similar to how large language models (like GPT) generate text word by word. The image is broken into tokens (small patches), and the model predicts each next token based on all previous tokens.

Think of it like writing a story: each word is chosen based on everything that came before it. Autoregressive image models do the same thing, but with visual patches instead of words. They build the image from top-left to bottom-right (or in a learned order), with each patch informed by the complete context of all previous patches.

Strengths

• Global coherence: Because each patch considers all previous patches, the overall image tends to be more coherent — fewer “conflicting details” in different parts of the image
• Photorealism: Autoregressive models often excel at photorealistic output, producing images that look remarkably like real photographs
• Speed: Can be very fast, especially with optimized architectures. BitDance generates high-quality images in seconds
• Text integration: Natural alignment with language models means strong prompt understanding

Weaknesses

• Sequential generation: Must generate patches in order — can’t easily parallelize like diffusion models
• Less artistic flexibility: Tend to favor photorealistic styles over artistic or abstract output
• Token artifacts: Can sometimes show subtle grid-like patterns from the patch tokenization

BitDance on Apefx

BitDance (4 credits, fast) is an autoregressive LLM-based image generator. It excels at:

• Photorealistic portraits and scenes
• Product photography
• Any use case where “looks like a real photo” is the goal
• Fast generation at an extremely competitive price

Transformer-Based Models

Examples on Apefx: Recraft V4 Pro, Grok Imagine

How They Work

Transformer models use the “attention mechanism” — the same technology that powers ChatGPT — to process images. They look at the entire image and text prompt simultaneously, identifying which parts of the prompt relate to which parts of the image.

Many modern image models are actually hybrids — they use transformers within a diffusion framework (DiT: Diffusion Transformer). The transformer handles the “understanding” while diffusion handles the “generation.” Recraft V4 Pro uses this hybrid approach, optimized specifically for design and marketing output.

Strengths

• Compositional understanding: Transformers excel at understanding spatial relationships and complex scenes
• Design quality: Particularly strong at clean, professional, design-ready output
• Typography: Often better at rendering text and design elements within images
• Scalability: Transformer architectures scale well with more compute and data

Weaknesses

• Compute intensive: Transformers require significant computational resources
• Specialized: Often optimized for specific use cases rather than being general-purpose

Recraft V4 Pro

Recraft V4 Pro (8 credits, medium) is a transformer-based model designed specifically for design and marketing:

• Clean, production-ready compositions
• Excellent typography and text placement
• Brand asset generation (logos, icons, patterns)
• Marketing materials (social media, ads, banners)

Grok Imagine

Grok Imagine (7 credits, fast) from xAI takes a creative, less constrained approach. It often produces unexpected, imaginative interpretations of prompts that other models play safe on. Available in standard and unrestricted (🌶️) modes on the Pro plan.

Speed vs Quality Tradeoffs

There’s a fundamental tension between speed and quality in AI image generation:

The most efficient workflow uses multiple speed tiers: instant previews for exploration, fast models for iteration, and premium models for final output. This is only possible on a multi-model platform like Apefx — single-model platforms give you one speed-quality option.

Model-by-Model Comparison

When to Use Which Model

• “I need it now” → Flux 2 Klein (1 credit)
• “It needs to look like a photo” → BitDance (4 credits)
• “Just give me something good” → Flux Pro (5 credits)
• “It needs text in the image” → Nano Banana 2 (8 credits)
• “It’s for a design/marketing project” → Recraft V4 Pro (8 credits)
• “Make it weird/creative” → Grok Imagine (7 credits)
• “This is the hero image” → Nano Banana Pro (15 credits)

The beauty of a multi-model platform is that you don’t have to commit. Try the same prompt on 3 different models and pick the best result. With Flux 2 Klein costing just 1 credit, experimentation is practically free.

For a hands-on introduction to getting started, see our complete beginner’s guide.