Google Gemini 3.5 Flash (1M) vs xAI Grok 3.5 (256k)
Side-by-side comparison of pricing, context window, capabilities, and a real-cost sample workload.
Option A
Google Gemini 3.5 Flash (1M)
by Google
Context: 1M
Input: $1.50 / 1M
Output: $9.00 / 1M
Released: 2026-05
Option B
xAI Grok 3.5 (256k)
by xAI
Context: 256K
Input: $5.00 / 1M
Output: $25.00 / 1M
Released: 2026-03
Detailed Comparison
| Dimension | Google Gemini 3.5 Flash (1M) | xAI Grok 3.5 (256k) |
|---|---|---|
| Provider | xAI | |
| Context window Winner | 1M | 256K |
| Input price ($/1M) Winner | $1.50 | $5.00 |
| Output price ($/1M) Winner | $9.00 | $25.00 |
| Sample workload cost Winner 1M input + 500K output tokens
|
$6.00 | $17.50 |
| Released Winner | 2026-05 | 2026-03 |
| Tokenizer | gemini | grok |
The verdict
On the dimensions we measured, Google Gemini 3.5 Flash (1M) wins more often - particularly on cost-effectiveness for a typical 1M+0.5M workload.
Google Gemini 3.5 Flash (1M) - Key features
Google's newest fast model (Google I/O 2026), built for agentic tasks and coding - beats Gemini 3.1 Pro on coding and agentic benchmarks at a fraction of the cost.
- Fast, low-cost agentic model
- 1M token context window
- Strong coding benchmarks
- Multimodal input
- Great price/performance
xAI Grok 3.5 (256k) - Key features
xAI's latest flagship model with expanded context, improved reasoning, and deeper integration with real-time data from X platform.
- 256K token context window
- Advanced reasoning and coding
- Real-time information access
- Trained on expanded Colossus cluster
- Improved multimodal capabilities
How to choose
- Pick the cheaper model if your workload is mostly straightforward classification, extraction, or summarization.
- Pick the bigger context if you process long documents, large codebases, or multi-document research.
- Pick the more recent release if you need state-of-the-art reasoning quality and don't mind paying a bit more.
- Use both via a routing layer - send simple tasks to the cheaper one and complex tasks to the smarter one. This is the highest-ROI optimization in production AI.
Estimate the real cost of either model for your prompts using our Token Calculator.