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OpenAI's new "o1" Model: When to Use It and When Not to

Last updated 22 June 2026 Published 15 September 2024

OpenAI's o1 was the first of a new kind of model - one that reasons before it answers. The specifics here are a September 2024 snapshot, but the decision it forces is evergreen: when is slow, careful reasoning worth it, and when do you want fast and cheap instead?

o1's "chain-of-thought" reasoning breaks complex problems into smaller steps, working through them like a human expert.

That makes it excellent for detailed, multi-step problems - and overkill for plenty of everyday tasks. Here's how I decide, after testing it on real work.

01The test: feedback on a book manuscript

I gave o1 two full chapters of my book and asked for line-by-line editorial feedback. It thought for 62 seconds before replying (unusually long - most responses came back in 5-10 seconds).

// what "thinking for 62 seconds" looked like

A glimpse of its visible reasoning: "Reading and analysing... mapping the request to OpenAI's policies... noting the engaging anecdotes and conversational tone... combining sentences for a more cohesive introduction... reducing redundancy and a grammatical issue... ensuring a clean, engaging storytelling flow." Dozens of steps like these, then a structured set of specific, located suggestions.

The feedback was incredibly detailed, and genuinely useful - I implemented several of the suggestions.

02Where o1 earns its slowness

The reasoning models shine when an expert could solve it - just not quickly.

use it for
Complex problem-solving

Step-by-step challenges: debugging multi-step code, large sequential problems like physics or health-data analysis.

use it for
Creative problem-solving

Working iteratively through options - product development, long-term strategy - testing approaches before committing.

use it for
Education and tutoring

It shows the reasoning, not just the answer - breaking a problem into steps and explaining each, which is where the learning is.

use it for
High-stakes fields

Where mistakes are costly - healthcare, aviation - the careful, step-by-step approach is worth the extra time.

When to stick with a faster model

For these, GPT-4o or Claude 3.5 Sonnet are the better call - speed beats depth.

Quick answers
FAQs, general Q&A, basic info - fast, without deep reasoning.
Content & marketing
Blog posts, copy, social - creative, flowing text generated quickly.
Conversational AI
Chatbots and assistants - smoother real-time dialogue, no reasoning delay.
Summaries
Pulling key points from a long document, light data analysis.
Time-sensitive
Live customer chats and anything where fast, real-time answers matter most.

03How to choose

Is the task complex and multi-step? Go with a reasoning model - it's built for careful, step-by-step work.
Do you need speed? Use a fast model. Most people won't reach for a reasoning model for everyday tasks.
Are the stakes high? The slow, careful approach is worth the wait when accuracy is essential.
Need creativity or conversation? Stick with a fast model for content and smooth dialogue.

Usage limits (Sept 2024 snapshot): OpenAI capped o1-preview at 30 messages a week (50 for o1-mini) on Plus/Team. Limits like these have eased over time, but reasoning models remain more expensive and rate-limited than fast models - plan accordingly.

Reasoning models are for problems an expert could solve - just not quickly.

For everything else - speed, creativity, conversation - a fast model wins. Match the model to the job.

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