From 4o to 5: A Technical Deep Dive into OpenAI's Latest Flagship Models
Well, it finally happened. After months of speculation & internet hype, OpenAI dropped their new flagship model, GPT-5. And let me tell you, the dust is still settling. For those of us who live & breathe this stuff, it’s been a whirlwind. The new model started rolling out, & just like that, a bunch of the older models we've gotten used to, including the impressive GPT-4o, are being phased out.
It’s a pretty big deal. GPT-4o felt like a game-changer just a short while ago, so what exactly does GPT-5 bring to the table? Is it just a minor step up, or are we talking a whole new ballgame? Honestly, it's a bit of both. Let's get into the nitty-gritty of what's changed, what hasn't, & what it all means for developers, businesses, & casual users alike.
First off, OpenAI is not being shy about this. They're calling GPT-5 a massive leap in intelligence, & for once, the marketing fluff seems to have some serious substance behind it. Sam Altman even went as far as calling it a "PhD-level expert" in a bunch of different fields. That's a bold claim, but the benchmarks seem to back it up.
Let's talk numbers for a second, because they're pretty staggering.
On the AIME 2025 math test, a benchmark for mathematical reasoning, GPT-5 scored an incredible 94.6% without using any external tools. For comparison, GPT-4o was at 71%. That’s a HUGE jump. In the world of software engineering, the difference is even more stark. On the SWE-bench Verified test, which measures how well a model can handle real-world software engineering tasks, GPT-5 scored 74.9%. GPT-4o? A mere 30.8%.
This isn't just about acing tests, though. It translates to real-world capabilities. The new reasoning engine in GPT-5 is just… better. It gets nuance, it can follow incredibly complex instructions, & it can produce structured outputs more reliably than any of its predecessors. Think about drafting legal documents or creating a full-blown health rehabilitation plan with just a few prompts. That's the kind of power we're talking about here.
Another major promise is a reduction in hallucinations. OpenAI claims GPT-5 is 45% less likely to have a factual error in its responses compared to GPT-4o. This is a big deal for anyone trying to use these models for serious research or business applications where accuracy is paramount. Fewer made-up facts means more reliable outputs, which is something we've all been waiting for.
The New Lineup: A Unified, But Specialized, Family
OpenAI has also streamlined their model family. It's a bit of a shake-up, but it makes a lot of sense. Essentially, GPT-5 is the new default for all ChatGPT users, from free to enterprise tiers. The older models, like GPT-4o, GPT-4.1, & the o3 series, are being retired.
Here’s a quick breakdown of how the new models map to the old ones:
- GPT-4o is now gpt-5-main
- GPT-4o-mini is now gpt-5-main-mini
- OpenAI o3 is now gpt-5-thinking
There’s also a new beast called GPT-5 Pro, which is currently only available for the top-tier subscribers. This model uses something called "parallel test time compute" & boasts even higher accuracy, making 22% fewer major errors than the standard GPT-5's "thinking mode" on tough tasks.
One of the most interesting architectural changes is the introduction of a "real-time router." This is an intelligent system that automatically analyzes your conversation & decides whether to use a quick-response model for simple queries or engage the deeper "GPT-5 thinking" mode for more complex problems. It's a clever way to optimize for both speed & power, without the user having to manually switch between models.
For businesses, this new, smarter architecture opens up a world of possibilities. Imagine having a customer service chatbot that can handle simple queries in a flash but can also seamlessly escalate to a deeper, more analytical mode to troubleshoot complex technical issues. This is where platforms like Arsturn come into play. By leveraging these powerful new models, Arsturn helps businesses build no-code AI chatbots trained on their own data. These bots can provide instant, 24/7 customer support, answer complex questions with newfound accuracy, & engage with website visitors in a way that feels incredibly human & intelligent. The ability of GPT-5 to switch between quick & deep thinking could make these interactions more efficient & satisfying than ever before.
Multimodality: A Tale of Two Models
When GPT-4o launched, its real-time voice & emotional expression capabilities were mind-blowing. It could sing, laugh, & carry on a conversation with a naturalness we'd never seen before. Here's the thing: GPT-4o is still the king of real-time voice interaction. GPT-5, in its current form, doesn't focus on live audio input/output.
So, if you're looking for a hands-free, voice-first experience, GPT-4o remains the go-to.
However, where GPT-5 REALLY shines is in visual & video understanding. It achieved an impressive 84.2% on the MMMU benchmark (which tests multimodal understanding) & 81.1% on VideoMMMU. This makes it incredibly powerful for analyzing charts, giving feedback on UI mockups, or even summarizing the content of a video. For developers & designers, this is a massive upgrade.
The Creative & Coding Revolution
The improvements aren't just for data nerds & analysts. Creatives & coders are getting a major boost too.
For the Writers:
OpenAI is calling GPT-5 its "most capable writing collaborator." The model is said to be better at turning rough ideas into compelling prose with real literary depth. The examples OpenAI released show a clear difference. Where GPT-4o might produce a poem with a predictable structure, GPT-5 crafts something with stronger imagery & more striking metaphors.
However, the user reviews on social media are a bit more mixed. Some users praise its narrative consistency & improved flow, while others feel it's less creative than GPT-4o, struggling with character consistency & producing shorter, less emotionally resonant responses. It seems that while it may be technically a better writer, it might have lost some of the "personality" that made 4o so beloved.
For the Coders:
This is where things get REALLY exciting. GPT-5 is, without a doubt, the most powerful coding model OpenAI has ever released. The leap from GPT-4o is significant. Real-world developers are reporting that GPT-5 can:
- Create complete, functional applications from a single prompt.
- Understand & implement complex architectural patterns.
- Generate aesthetically pleasing UI with a good sense of spacing & typography.
- Debug large codebases with multiple dependencies.
It can essentially create responsive websites, apps, & even games from natural language prompts, drastically lowering the barrier to entry for people without coding skills. This could fundamentally change how we approach web & app development.
For businesses, this means more efficient development cycles & the ability to prototype ideas faster than ever. It also has huge implications for website engagement. Imagine using an AI to not only chat with customers but to actively help them build or customize products in real-time. This is the kind of advanced functionality that conversational AI platforms are moving towards. With Arsturn, for example, a business could create a custom AI chatbot that not only answers questions but guides users through complex configuration processes, leveraging GPT-5's powerful coding & reasoning abilities to create a truly interactive & personalized customer experience. This could be a game-changer for lead generation & boosting conversions.
Let's Talk Money: The New Pricing Structure
OpenAI is getting aggressive with its pricing, which is great news for pretty much everyone. GPT-5 is priced at half the input cost of GPT-4o, while the output cost remains the same.
Here's a quick look at the numbers:
- GPT-5: $1.25/million input tokens, $10/million output tokens
- GPT-5 Mini: $0.25/million input tokens, $2.00/million output tokens
- GPT-5 Nano: $0.05/million input tokens, $0.40/million output tokens
One thing to note is that the "invisible reasoning tokens" used by the new
mode count as output tokens, so you might see higher output usage on complex prompts. However, they've also introduced a 90% discount on cached input tokens, which is a huge deal for chat applications where the same conversation history is sent with every new message.
So, What's the Verdict?
Honestly, GPT-5 is a monumental release. It's not just an incremental update; it feels like a foundational shift. The raw intelligence & reasoning power are on another level, especially in technical domains like math & coding. The reduction in hallucinations & the new, more robust architecture make it a far more reliable tool for serious, real-world applications.
But it's not a clear-cut "better in every way" situation. GPT-4o still holds the crown for real-time, expressive voice conversations. And there's a legitimate debate to be had about whether GPT-5 has lost some of the creative spark & personality that made 4o feel so special.
For businesses, the implications are massive. The ability to build more intelligent, more reliable, & more capable AI assistants is here. Whether it's for customer service, lead generation, or internal automation, the power of GPT-5 is going to unlock new levels of efficiency & engagement. Platforms that help businesses harness this power, like Arsturn, which allows for the creation of no-code AI chatbots trained on a company's own data, are going to be more valuable than ever. Building meaningful, personalized connections with your audience through these advanced AI tools is no longer a futuristic dream; it's the new standard.
At the end of the day, GPT-5 is a robust, safety-first system that democratizes access to expert-level intelligence. It's faster, smarter, & more useful for a huge range of tasks. While we might miss some of the quirks of GPT-4o, there's no denying that the future of AI just took a pretty big leap forward.
Hope this was helpful & gave you a good sense of what's what in this new AI landscape. It's a lot to take in, but it's also incredibly exciting. Let me know what you think