Gemini 3.5 Review: Is Google's 'Frontier Intelligence with Action' Better Than GPT-5 Pro?

On May 19, 2026, Google dropped Gemini 3.5 — its most significant model update since Gemini 2 Ultra. The headline promise is 'frontier intelligence with action,' which translates to deeper agentic workflows, native multi-turn tool use, and a 2-million-token context window that finally feels usable. Within 48 hours, it became the most talked-about AI release of the month. We spent a week running the same eight real-world tasks through Gemini 3.5, GPT-5 Pro, and Claude 4.5. Here's what we found — and which model actually wins.

What Gemini 3.5 Actually Brings to the Table

Google DeepMind isn't just shipping a smarter chatbot. Gemini 3.5 is designed as an action engine: it plans, it calls tools, it observes results, and it loops back to adjust. The 'action' part means Gemini can now hold a long-running task across Google Workspace, Maps, Flights, and third-party APIs without losing state.

• 2M-token context window with near-linear attention scaling.
• Native agentic loop: plan → act → observe → replan.
• Deeper Google Workspace integration: Docs, Sheets, Gmail, Calendar, Drive.
• Gemini 3.5 Flash API at $1.50 per million input tokens, 1M context.
• Multimodal reasoning across video, audio, images, and code in a single session.

Test 1: Complex Multi-Step Research

We asked each model to research, compare, and summarize the top four project-management tools for a 50-person remote team, then build a weighted scoring rubric and output a final recommendation.

Gemini 3.5 won on speed and source diversity. It pulled live pricing from four vendor sites, read recent Reddit threads, and checked G2 reviews — all within the same session. GPT-5 Pro produced a more nuanced strategic analysis but required two human nudges to complete the scoring rubric. Claude 4.5 wrote the most readable summary but missed two 2026 pricing changes.

Test 2: Coding a Real Feature From a Figma Spec

We exported a Figma auto-layout spec for a dashboard widget and asked each model to generate a working React + Tailwind component. Gemini 3.5's new visual reasoning parsed the Figma JSON accurately, produced responsive code, and even suggested accessibility fixes. GPT-5 Pro's code was cleaner but required manual breakpoint adjustments. Claude 4.5 wrote the most maintainable TypeScript but missed one spacing detail from the spec.

Test 3: Writing with Voice and Tone

Claude 4.5 remains the best writer of the three. Gemini 3.5's drafts improved noticeably over Gemini 2 Ultra — less corporate, more rhythmic — but still needed a heavier editing pass. GPT-5 Pro sits in the middle: reliable, readable, rarely surprising. If your job is words, Claude is still the tool.

Gemini 3.5 is the fastest researcher, GPT-5 Pro is the most reliable generalist, and Claude 4.5 is still the best writer. The gap is narrowing, but the shape of each model hasn't changed.

Test 4: Agentic Task Completion

This is where Gemini 3.5's 'action' branding shows up. We asked it to plan a three-city European trip for two people with a €2,500 budget, including flights, hotels, and a daily restaurant shortlist, then create a shared Google Doc itinerary and add calendar holds.

Gemini completed the entire chain: searched flights on Google Flights, compared hotels, built the Doc, shared it, and added calendar events. It took one correction ('avoid Ryanair') and handled the rest. Neither GPT-5 Pro nor Claude could complete the full chain without human intervention at multiple steps.

Pricing and Access (May 2026)

• Gemini 3.5: included in Gemini Advanced ($20/mo); API via Google AI Studio.
• Gemini 3.5 Flash API: $1.50/M input tokens, $6/M output tokens, 1M context.
• GPT-5 Pro: $20–$200/mo via ChatGPT; API tiered by organization.
• Claude 4.5: $20–$100/mo via Claude Pro/Max; API standard + extended pricing.

The Verdict: Who Should Switch?

• Switch to Gemini 3.5 if you live in Google Workspace and want an agent that actually finishes multi-step jobs.
• Stick with GPT-5 Pro if you want one model that does almost everything reliably well.
• Keep Claude 4.5 if writing quality, tone, and long-form drafts matter most to your work.

What's Coming Next

Google has already teased Gemini 3.5 Pro with a 4M context window and deeper third-party API partnerships. Anthropic is expected to respond with Claude 5 this summer, and OpenAI's GPT-5 Omni is rumored for a fall launch. The pace isn't slowing — but for now, Gemini 3.5 is the most capable action-oriented model you can actually use today.

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Sources & References

• Google Gemini 3.5 announcement
• Google DeepMind