Gemini 3.5 Flash vs Claude Haiku 4.5: two fast models, different strengths

Most production traffic doesn't need a flagship. It runs on the fast, cheap tier, and the two usual picks there are Google's Gemini 3.5 Flash and Anthropic's Claude Haiku 4.5.

The short version: Gemini 3.5 Flash for speed, tool use and multimodal input, Claude Haiku 4.5 for lower cost and steady coding.

Specs and price

Prices are FastMetal's USD list as of October 26, 2026; current figures are on the models page. On a task of 100,000 input tokens and 10,000 output tokens, that's about $0.26 on Gemini 3.5 Flash and $0.18 on Haiku 4.5. Output is where the gap is: Gemini costs about 1.7 times as much per output token.

Where each is stronger

Gemini 3.5 Flash is about speed and tools. It was reported at about 278 tokens per second, pitched as Pro-level reasoning at Flash speed, and it came out first on multi-step tool use over MCP at 83.6%, ahead of Claude Opus 4.7 and GPT-5.5. Google's model also takes video; on FastMetal it accepts text, images, PDFs and audio.

Claude Haiku 4.5 is about cost and steady code. It's the cheaper of the two and runs at more than twice the speed of the Sonnet models. Its 73% on SWE-bench Verified puts its code at a quality you can put through review. Early developers said the speed changed how they worked, and many use it for most of their day-to-day work, sending only the hard cases up to a larger model.

Weak spots

Gemini 3.5 Flash: the price went up, and it's not a Pro model. Developers complained that output pricing roughly tripled from the previous generation. On real-world code it was reported behind Claude Opus 4.7 on SWE-bench Pro, so treat it as a fast model, not a Pro-class one. There are also reports that it uses a lot of resources and ranks lower on some workloads, Android development among them.

Claude Haiku 4.5: narrower input, lower ceiling. It reads text and images only, with no audio or video. On the hardest tasks, Sonnet and Opus are clearly ahead.

Which to use where

• Gemini 3.5 Flash: tool-heavy agents, multimodal pipelines with images or audio, and chat where response speed matters most.
• Claude Haiku 4.5: coding on a budget, and high-volume workloads where it does the bulk of the work and only the hard cases go to a larger model.

Try both with one key

On FastMetal both are behind the same API key and the same balance. Change model and nothing else.

# Gemini 3.5 Flash
curl https://api.fastmetal.ai/v1/chat/completions \
  -H "Authorization: Bearer $FASTMETAL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "gemini-3.5-flash", "messages": [{"role": "user", "content": "Hello"}]}'

# Claude Haiku 4.5: same request, different model
curl https://api.fastmetal.ai/v1/chat/completions \
  -H "Authorization: Bearer $FASTMETAL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "anthropic-claude-haiku-4-5", "messages": [{"role": "user", "content": "Hello"}]}'

The side-by-side comparison page has both models' answers to the same prompts.

FAQ

Which is cheaper? Claude Haiku 4.5: $1.17 in and $5.81 out per million tokens on FastMetal, against $1.65 and $9.90 for Gemini 3.5 Flash. Current prices are on the models page.

Which should I use for multimodal work? Gemini 3.5 Flash. On FastMetal it takes images, PDFs and audio as well as text. Haiku 4.5 takes text and images.

Which is better outside English? We couldn't find a published benchmark that isolates non-English quality for either model. If your work is mostly in another language, test with your own prompts.

Public benchmarks only narrow the field. The reliable way to choose between two models this close is to run both on a sample of your own tasks and score the results.