ChatGPT From AZ: All Models and How to Get the Most Out of AI

Over time, OpenAI has continued to evolve and add new AI models to the ChatGPT ecosystem. From the traditional large language models (LLMs) of the GPT family, to the next generation of reasoning models (o-series), each version aims to serve an increasingly diverse range of user needs and use cases.

The flexibility to choose the right model according to your needs is a strong point, but this also unintentionally creates a lot of confusion for ordinary users: Which model should I use? What are the strengths and weaknesses? When should I use o3, when should I choose GPT-4o? To fully answer these questions, in this article, SaDesign will analyze in detail all the existing ChatGPT models, their advantages, limitations and specific suggestions on how to make the best use of each model. Let's start this journey of learning from the most powerful model today: o3.

1. ChatGPT o3 Model

If you are looking for an AI model that can reason and solve the most complex problems, then o3 is OpenAI's top choice today.

The o3 model belongs to the generation of agentic reasoning, which means it not only answers questions in the form of "memorization" or "text creation", but also automatically thinks, analyzes logic, and even automatically activates additional tools inside ChatGPT such as Python code interpreter, web browser, file analysis, image processing, etc. to give comprehensive responses.

Another great advantage of o3 is its powerful multimodality. You can upload images, diagrams, charts or documents, and the model will analyze the visualization to understand the context. The visual precision of o3 allows it to identify locations, objects, and analyze visual data.

Therefore, o3 is especially suitable for STEM tasks: Mathematics, Science, Technology, Engineering. You can absolutely ask difficult questions, requiring thinking models for a few minutes to find the best solution.

However, please note: The o3 model is only available to paid users (ChatGPT Plus or Pro plans). You can easily switch to o3 using the drop-down menu in the ChatGPT interface, select the right model to start an advanced brainstorming session.

2. ChatGPT 4o Model

Next, we come to GPT-4o, which is the default model and also the “backbone” of the entire current ChatGPT platform.

GPT-4o isn't the most powerful model in reasoning, but it's the most versatile and comprehensive. It's a traditional LLM, optimized by OpenAI for natural conversation, responding quickly and smoothly in real-life conversations.

If you need creative writing, text summarization, translation, or everyday questions, GPT-4o will outperform the o-series reasoning models. It's also multimodal: You can upload images, and GPT-4o will describe, analyze, and respond.

Another interesting point: GPT-4o is the “foundation” for many of ChatGPT’s innovative features. From the original image generation tool, to the advanced voice mode and Live Video, everything is powered by GPT-4o.

For example, the recent Ghibli viral image or the camera and screen sharing feature for real-time AI interaction are all handled by GPT-4o. In addition, GPT-4o also analyzes files, data, runs basic Python code, and serves as the foundation for custom GPTs.

Biggest plus: GPT-4o is available for both free and paid users. With the Free plan, you still get basic GPT-4o. When you exceed the limit, ChatGPT automatically switches to GPT-4o mini, a more compact version that still maintains stable conversation quality.

3. ChatGPT 4.5 Model

If GPT-4o is a versatile “conversation buddy”, then GPT-4.5 is a “text generation master”.

GPT-4.5 is the largest non-reasoning LLM model OpenAI has ever built, and is currently in Research Preview. Access is limited to paid users.

The core difference of GPT-4.5 lies in its ability to grasp deeper context, higher EQ, and more natural and humorous interactions than other models. It can recognize complex patterns from prompts, draw creative connections, and generate “human” text.

Thanks to that, GPT-4.5 is extremely suitable for those who write blogs, write scripts, come up with marketing ideas, edit long-form content or any situation that requires subtle emotions and creativity.

One thing to note: GPT-4.5 is not available in the API because the model size is quite large, OpenAI only makes it available in ChatGPT for “More Models” subscribers.

4. ChatGPT o4-mini

If o3 is the "big guy" in terms of reasoning ability, o4-mini is the "small version" that is more compact, intelligent and economical that OpenAI brings to all users, even for free.

The o4-mini's strengths lie in its ability to handle mathematical, cryptographic, and visualization tasks quickly and efficiently, with performance that can even surpass the o3 in some real-world scenarios such as debugging code or solving short math problems. Despite its small size, the o4-mini maintains an agentic reasoning philosophy, meaning it can enable the auxiliary tools in ChatGPT: from running Python, browsing the web, downloading and parsing files, to reading and understanding charts.

In particular, o4-mini has replaced the previous o3-mini on the free ChatGPT package. Users can simply click the “Extended thinking” button to unlock advanced reasoning power at no cost. With low operating costs and fast response speed, o4-mini is extremely suitable for those who need a mid-range STEM assistant, solve math problems, write code, and check formulas without needing the “full” o3.

Point to remember: due to its optimized design, o4-mini is better suited for short or step-by-step questions than super long reasoning chains. But compared to GPT-4o, o4-mini still has a clear advantage when it comes to more complex problems that require logical thinking.

In short, if o3 is for high-level theorists, o4-mini is an affordable choice, powerful enough to solve difficult problems quickly, especially useful for ChatGPT Free users.

5. ChatGPT Model 4.1

While the o-series focuses on reasoning and GPT-4.5 is more about creativity, GPT-4.1 is a “code expert” that OpenAI developed specifically for programmers who want fast, low-cost performance while still handling large projects.

GPT-4.1 was initially available as a private API for developers, but is now available in ChatGPT for paid users. This model does not use circular reasoning, but is optimized for high-speed coding, with a super-large context window (up to 1 million tokens). Thanks to this, you can upload long code files, debug, edit modules without worrying about "breaking the thread" like with small models.

GPT-4.1 is also updated with new programming knowledge, supporting many modern frameworks and libraries. In addition to the full version, OpenAI also has GPT-4.1 mini/nano for small dev teams to save costs while still achieving efficiency.

Strengths: Writing code, debugging, refactoring, analyzing complex logic, all faster and cheaper than using o3 or o4-mini just for coding. However, you need a ChatGPT Plus or Pro account to access GPT-4.1.

In short, if you are a developer, GPT-4.1 is the ideal "programming assistant": strong in coding, cost-effective, supports long projects, suitable for both corporate and freelance teams.

6. ChatGPT o1 pro model

Before the o3 and o4-mini, the o1 pro was the top choice for those who needed deep AI reasoning, especially in math, programming, and scientific research. This was the first generation of agentic reasoning models, notable for its “sitting and thinking” ability, meaning it was willing to spend more computational time analyzing carefully, instead of responding quickly like conversational models.

Thanks to that, o1 pro is trusted by experts, researchers, engineers for long logic questions, analyzing complex formulas or debugging difficult code. The only downside: high operating costs, only available in the ChatGPT Pro package, priced up to 200 USD/month.

Today, with the advent of the o3 (more powerful) and o4-mini (faster, lighter), the o1 pro is becoming less popular. However, OpenAI still maintains it as a stable “deep reasoning mode” for those who need it. Soon, the o3 pro will replace the o1 pro, promising to combine long-term reasoning with more speed and powerful tools.

In short, the o1 pro is still worth it if you really need AI to analyze difficult problems, reason long-term, accept long waits and high costs, but otherwise, the o3 or o4-mini is powerful enough for most practical reasoning needs.

7. Codex-1 Model

In addition to the “big guys” in conversation and reasoning, OpenAI also has Codex-1 - a high-end “dev assistant” specifically for programmers. Codex-1 was developed from o3, but has been refined to focus entirely on software tasks: writing code, adding features, running tests, creating pull requests, automating workflows.

Codex-1 not only generates individual codes, but can also understand project logic, detect potential errors, propose optimizations, and suggest refactorings thanks to being trained using reinforcement learning (RL) with a huge amount of real-world coding data.

What's special is that Codex-1 doesn't appear directly in the main chat window, but operates through the ChatGPT sidebar or dedicated technical AI agents, which you need the Plus or Pro plan to access.

If GPT-4.1 is strong in fast coding, Codex-1 is stronger in the ability to "work in teams" with developers: understand the idea, run tests, track logic, and propose CI/CD processes. This is an ideal tool for software development teams, startups, and freelancers who need AI to really "work side by side".

In short, Codex-1 is like a smart “dev assistant”: writing code, checking, editing, testing all automatically, saving hours of keyboard typing. As long as you are willing to open a paid wallet, you will unlock a coding AI that is more advanced than GPT-4.1.

Hopefully this article has given you a comprehensive overview of all ChatGPT models and how to use them most effectively. No matter which model you choose, the most important thing is: Understand your purpose clearly, thereby activating the most suitable "AI brain". Wish you to exploit the power of ChatGPT to the fullest, turn it into a smart, powerful AI assistant and worth every penny invested!