Gemini 3.1 Pro Preview Custom Tools vs GPT-3.5 Turbo 16k

GPT-3.5 Turbo 16k costs 3.0x less per output token than Gemini 3.1 Pro Preview Custom Tools ($4.00 vs $12.00 per million). Updated October 22, 2026; no benchmark has tested both models yet.

Replace Gemini 3.1 Pro Preview Custom Tools Replace GPT-3.5 Turbo 16k

Gemini 3.1 Pro Preview Custom ToolsGoogle

Coding: No data
Overall: No data
Output $/M: $12.00

GPT-3.5 Turbo 16kOpenAI

Coding: No data
Overall: No data
Output $/M: $4.00

vs $12.00 vs $4.00 per 1M output tokens. GPT-3.5 Turbo 16k is 3.0x cheaper.

Gemini 3.1 Pro Preview Custom Tools or GPT-3.5 Turbo 16k: which to pick

Neither model has a coding score yet, so the two cannot be ranked on coding.

Pick Gemini 3.1 Pro Preview Custom Tools for a larger context window (1.05M against 16K tokens).

Model AGemini 3.1 Pro Preview Custom ToolsGoogleNot benchmarkedNo coding benchmarkNo cost per solved task Model BGPT-3.5 Turbo 16kOpenAINot benchmarkedNo coding benchmarkNo cost per solved task

No benchmark has tested both yet. Gemini 3.1 Pro Preview Custom Tools has results on Vending-Bench 2; GPT-3.5 Turbo 16k has none yet. Compare them on price and context instead.

Which one for your work

Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.

Coding
Vibe Coding Index, six public coding benchmarks
No call
Neither has a coding score yet.
One side not measured
Long documents
Listed context window
Gemini 3.1 Pro Preview Custom Tools
Gemini 3.1 Pro Preview Custom Tools takes 1.05M tokens against 16K.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
GPT-3.5 Turbo 16k
Gemini 3.1 Pro Preview Custom Tools $0.0080, GPT-3.5 Turbo 16k $0.0050 per turn.
List prices

At a glance

Coding index: Gemini 3.1 Pro Preview Custom Tools not benchmarked, GPT-3.5 Turbo 16k not benchmarked.
Widest category: None yet: no category has been tested on both models.
Widest single gap: None yet: no benchmark has tested both models.
Output price: Gemini 3.1 Pro Preview Custom Tools $12.00 against GPT-3.5 Turbo 16k $4.00 per million output tokens, 3.0x apart.
Context window: Gemini 3.1 Pro Preview Custom Tools takes 1.05M tokens, GPT-3.5 Turbo 16k 16K.

Benchmark by benchmark

Every board either model has a result on, a category to a fold; bars are each result on a 0 to 100 scale. Only one model is measured on each, so no row names a leader.

Agentic workDirectional onlyPublic boards, shown as published, kept out of the index1 board measured

Agentic work benchmarks for Gemini 3.1 Pro Preview Custom Tools and GPT-3.5 Turbo 16k
Benchmark	Gemini 3.1 Pro Preview Custom Tools	GPT-3.5 Turbo 16k	Leader
Vending-Bench 2	$3,774	Not measured	Only Gemini 3.1 Pro Preview Custom Tools measured
Neither model has a result on the other 41 boards here

What each workload costs

Three fixed token mixes at each model's listed price, so per-token rates become a bill.

Chat turn

1K input + 500 output tokens

Gemini 3.1 Pro Preview Custom Tools$0.0080Fits in one request

GPT-3.5 Turbo 16k$0.0050Fits in one request

GPT-3.5 Turbo 16k costs less

Repository review

50K input + 3K output tokens

Gemini 3.1 Pro Preview Custom Tools$0.136Fits in one request

GPT-3.5 Turbo 16k$0.162Exceeds the context window

Gemini 3.1 Pro Preview Custom Tools costs less

Agent loop

200K input + 10K output tokens

Gemini 3.1 Pro Preview Custom Tools$0.520Fits in one request

GPT-3.5 Turbo 16k$0.640Exceeds the context window

Gemini 3.1 Pro Preview Custom Tools costs less

Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.

Specification differences

The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.

Specifications of Gemini 3.1 Pro Preview Custom Tools and GPT-3.5 Turbo 16k
Specification	Google Gemini 3.1 Pro Preview Custom Tools	OpenAI GPT-3.5 Turbo 16k
Maker	Google	OpenAI
Weights	No public weights listed	No public weights listed
Released	February 25, 2026	August 28, 2023
Context window	1.05M	16K
Input $/Mtok	$2.00	$3.00
Output $/Mtok	$12.00	$4.00
Coding index	Not benchmarked	Not benchmarked
Independent measurements behind it	0	0
Cost per solved task	Not computable	Not computable
Source	OpenRouter listing	OpenRouter listing

Questions

Is Gemini 3.1 Pro Preview Custom Tools better than GPT-3.5 Turbo 16k for coding?

Neither model has a coding score yet, so the two cannot be ranked on coding. Pick Gemini 3.1 Pro Preview Custom Tools for a larger context window (1.05M against 16K tokens).

Which is cheaper, Gemini 3.1 Pro Preview Custom Tools or GPT-3.5 Turbo 16k?

Gemini 3.1 Pro Preview Custom Tools costs $2.00 per million input tokens and $12.00 per million output tokens; GPT-3.5 Turbo 16k costs $3.00 and $4.00. Cost per solved task is known for neither of them.

Which has the bigger context window, Gemini 3.1 Pro Preview Custom Tools or GPT-3.5 Turbo 16k?

Gemini 3.1 Pro Preview Custom Tools, with 1.05M tokens against 16K.

Has any benchmark tested both Gemini 3.1 Pro Preview Custom Tools and GPT-3.5 Turbo 16k?

No benchmark has tested both yet. Gemini 3.1 Pro Preview Custom Tools has results on Vending-Bench 2; GPT-3.5 Turbo 16k has none yet. Compare them on price and context instead. Data as of October 22, 2026.