GPT-4 Turbo vs Step 2 (16K) vs Sonar Pro
Too close to call on our weighted score (Sonar Pro 20, GPT-4 Turbo 20, Step 2 (16K) 11). The right pick depends on what you value most.
OpenAIGPT-4 Turbo
20/100- ECI—
- Price$10.00 / $30.00
- Context128K
StepFunStep 2 (16K)
11/100- ECI—
- Price$5.21 / $16.44
- Context16K
PerplexitySonar Pro
20/100- ECI—
- Price$3.00 / $15.00
- Context200K
Too close to call
It is close. Our weighted score puts them within a point (Sonar Pro 20/100, GPT-4 Turbo 20/100, Step 2 (16K) 11/100), so choose by what matters most for your work: Sonar Pro on price and Sonar Pro for long inputs. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
- CapabilityNot enough dataNo independent benchmark covers every model here yet
- Lowest priceSonar ProSonar Pro $6.00 · Step 2 (16K) $8.02 · GPT-4 Turbo $15.00 per 1M tokens (3:1 blend)
- Longest contextSonar ProSonar Pro 200,000 · GPT-4 Turbo 128,000 · Step 2 (16K) 16,384 tokens
- Widest inputsGPT-4 Turbo and Sonar ProGPT-4 Turbo: Text, Images · Step 2 (16K): Text · Sonar Pro: Text, Images
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | GPT-4 Turbo | Step 2 (16K) | Sonar Pro |
|---|---|---|---|---|
| Price | 50% | 0 | 7 | 13 |
| Inputs & features | 30% | 50 | 25 | 25 |
| Context window | 20% | 24 | 0 | 32 |
| Overall | 100% | 20/100 | 11/100 | 20/100 |
Left out because at least one model lacks the data: capability. The remaining weights were rescaled.
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-4 TurboOpenAI | Step 2 (16K)StepFun | Sonar ProPerplexity |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | — | — | — |
| ECI rank | — | — | — |
| Price per million tokens | |||
| Input | $10.00 | $5.21 | $3.00 (best) |
| Output | $30.00 | $16.44 | $15.00 (best) |
| Cached input | — | $1.04 | — |
| Blended (3:1) | $15.00 | $8.02 | $6.00 (best) |
| Long-context rate | Same rate | Same rate | Same rate |
| Price source | Official OpenAI API | Official StepFun (Global) API | Official Perplexity API |
| Limits | |||
| Context window | 128,000 tokens | 16,384 tokens | 200,000 tokens (best) |
| Max output | 4,096 tokens | 8,192 tokens (best) | 8,192 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | No | Yes |
| PDFs | No | No | No |
| Audio | No | No | No |
| Video | No | No | No |
| Reasoning | No | No | No |
| Tool calling | Yes | Yes | No |
| Structured output | No | No | No |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gpt-4-turbo | step-2-16k | sonar-pro |
| API providers | 12 (best) | 1 | 5 |
| Released | Nov 6, 2023 | Jan 1, 2025 | Jan 1, 2024 |
| Knowledge cutoff | Dec 2023 | Jun 2024 | Sep 1, 2025 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GPT-4 Turbo$160.00
- Step 2 (16K)$84.98
- Sonar Pro$60.00
Which should you choose?
Which is better: GPT-4 Turbo, Step 2 (16K) or Sonar Pro?
It is close. Our weighted score puts them within a point (Sonar Pro 20/100, GPT-4 Turbo 20/100, Step 2 (16K) 11/100), so choose by what matters most for your work: Sonar Pro on price and Sonar Pro for long inputs. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.
Which is cheaper, GPT-4 Turbo, Step 2 (16K) or Sonar Pro?
Sonar Pro is cheaper at $3.00 input / $15.00 output per million tokens (official Perplexity API price). Step 2 (16K) costs $5.21 input / $16.44 output per million tokens (official StepFun (Global) API price); GPT-4 Turbo costs $10.00 input / $30.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $6.00 per million tokens for Sonar Pro versus $8.02 for Step 2 (16K) (1.3× as much) and $15.00 for GPT-4 Turbo (2.5× as much).
Which scores higher on benchmarks?
There is no independent benchmark that covers all three models yet. GPT-4 Turbo has not been scored yet, Step 2 (16K) has not been scored yet and Sonar Pro has not been scored yet.
Which is better for coding?
There are no published SWE-bench Verified results for GPT-4 Turbo, Step 2 (16K) and Sonar Pro yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Note that Sonar Pro does not support tool calling, which most coding agents need.
Which has the bigger context window?
Sonar Pro has the largest context window at 200,000 tokens, against 128,000 for GPT-4 Turbo and 16,384 for Step 2 (16K). Maximum output per response: GPT-4 Turbo up to 4,096, Step 2 (16K) up to 8,192, Sonar Pro up to 8,192 tokens.
Which can read images, PDFs, audio or video?
GPT-4 Turbo accepts text and images; Step 2 (16K) accepts text; Sonar Pro accepts text and images. GPT-4 Turbo handles the widest range of inputs.
Are any of these open source?
No. GPT-4 Turbo, Step 2 (16K) and Sonar Pro are proprietary and only available through APIs and apps.
Which is newer?
Step 2 (16K) is the newest, released Jan 1, 2025. Sonar Pro came out Jan 1, 2024; GPT-4 Turbo came out Nov 6, 2023. Knowledge cutoff: GPT-4 Turbo Dec 2023, Step 2 (16K) Jun 2024, Sonar Pro Sep 1, 2025.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
