All ChatGPT Models: Which One Should You Actually Use?

Last updated on November 20th, 2025 at 02:12 am

I understand, by the way, nine different models are listed in the dropdown on ChatGPT, and you just think, what is the difference between them? This was what also confused me until I took the time and tried each of them in various assignments. Here’s what I figured out.

The Current Lineup: What There Is at Present.

By November 2025, OpenAI implemented a relatively impressive library. There is the older GPT-3.5 that is still around and given free to users, up to the newer GPT-5.1 with its dual-model architecture. They are all constructed in a certain circumstance, and to be quite honest, it can be a waste of time to choose the wrong one.

The lineup will fall into a handful of categories. There are older models such as GPT-3.5, improved reasoning features such as GPT-4 and GPT-4.1, the multimodal GPT-4o dealing with images and voice, the expert reasoning models (the o-series) and the latest flagship model – GPT-5.1.

GPT-3.5: The Free Entry Point

Here is the point where majority of the individuals begin. GPT-3.5 was released in November 2022 and is not excluded of the free user, its context window has 4,096 tokens. It is okay when it comes to simple tasks, simple writing, and getting a sense of what AI is capable of doing.

However, there is a twist to it, it is clearly weaker than newer models. I attempted to use it to explain technical things and it continued giving superficial responses. Absolutely ideal in casual things, not in depth.

GPT-4 Series: Take the Night Off.

GPT-4 was released in March 2023, and GPT-4.1 in April 2025 when GPT-4.1 has a huge 1-million token context window. Not an increase in spec per se, but a significant increase in the scale at which you can throw entire codebases, legal documents and even research papers in to it and manage to make sense of them.

The GPT-4.1 was assessed on a 50-page technical text. It kept context all the way through and picked up details that I had overlooked. The model is good at programming and any activity that needs prolonged attention on lengthy documents.

GPT-4o: The All-Rounder

GPT-4o released in May 2025 and required text, voice, and visual understanding to be integrated into a single architecture of 128,000 tokens. This is what has set as the default setting of most ChatGPT users, and with reason.

What makes GPT-4o special? You would be able to upload psyches, request it to analyze diagrams, engage in voice conversations, or freely transition between pictures and text. I would upload error screenshots on it, which I would use to debug code, much faster than typing all the code out.

Deep Thinking Models: the o-Series.

O3 and o3-pro models focus on the logical reasoning and are based on 200,000 token-context window, are proficient at complex instructionaccompanied instructions and highly structured reasoning. They are constructed to perform an action that involves step intelligence.

I experimented with o3 in a multi-step problem of the type of legal contract analysis. It deconstructed every one of the clauses in a systematic way, and identified contradictions I had failed to notice. The catch? The reason is that it is slower, since in fact it is not merely pattern-matching but thinking through problems.

GPT-5 and GPT-5.1: The New Standard

Also in August 2025, GPT-5 was introduced and will automatically direct requests according to complexity, with GPT-5.1 released that same month in November 2025, which divides the model into two that are coordinated, Instant and Thinking.

And there is where it is interesting. GPT-5.1 Instant is more conversationally and less robotically inclined in handling everyday tasks, whereas GPT-5.1 Thinking is more focused on complex problem-solving, and is also about twice as speedy on the easy ones and twice as sluggish on the harder ones.

The system automatically selects the version to be used. In asking it to explain quantum mechanics it came into Thinking mode. For casual conversation? Instant kicked in. You don’t choose — it adapts.

Which Model Should You Actually Use?

To ask fast questions and to have a quick chat: Use GPT-5.1 Instant or GPT-4o. They are quick, talkative, and do not think hard on doing the majority of daily tasks.

In the case of coding projects: The context of GPT-4.1 is unsurpassed in millions of tokens. I am able to paste complete repositories and it is also aware of the connectivity of all things.

On complicated reasoning: The o-series models/ GPT-5.1 Thinking. Court documents, research, accounting, and so on – activities that demand a precise use of logic are best served by their slow pace.

To become creative: GPT-5.1 Instant with personality celebrity. The system has eight style choices with Friendly, Professional, Quirky, and Cynical and also has experimental fine-tuning features.

In dealing with image and voice tasks: GPT-4o is the only one that truly matters here. It is multimodally constructed and easily copes with it.

The Accuracy Reality Check

Here is one such item: a Deakin University study discovered that the GPT-4o generated does produce about 20 per cent of scholarly references, and more than five6 per cent include incorrect markers or are totally fraudulent. This is what I have observed myself- it quotes papers that are not in existence.

The important information must always be checked. These are effective models, and, still, they are fallible. I use them as intelligent aids that grow arrogant occasionally.

What About Cost?

ChatGPT has five plans: Free (GPT-5 limited), Plus (GPT-5 limited, GPT-4o limited, limited reasoning), Pro (unlimited access to all models), Team (25 -30/user/month), and Enterprise (varied pricing).

Most people find Plus, at $20/month, sweet. You are able to access sophisticated models at pocket friendly prices. I increased following daily restrictions on the free plan more than once.

The Bottom Line

You do not have to get into all the technicalities. Addition Choose a model Your simple stuff is handled with fast models, multifaceted issues with reasoning models, multimodal work is handled with GPT-4o, and enormous documents are handled with the large context window of GPT-4.1.

The system is becoming smarter as an interfering option-deciding system. The auto-routing feature of GPT-5.1 implies that you will simply raise questions and it will determine which brain to apply. That is the way it really ought to be.

Create a free version, determine what you are using it to do, and upgrade when you start using it to its limits. And bear in mind, these are instruments which multiply your powers, and not a substitution of your judgment. Essentially where precision is concerned.

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