General-purpose AI assistants have become an integral part of the grant writing process.
Researchers, consultants and proposal managers increasingly use ChatGPT, Claude and Gemini to brainstorm ideas, improve proposal sections, analyse call documents and refine technical writing.
Although these three AI assistants share many capabilities, they were not designed with exactly the same strengths. Understanding those differences can help you choose the right assistant for each stage of a Horizon Europe proposal.
At a Glance
ChatGPT
Claude
Gemini
Primary focus
General-purpose AI assistant
Long-form writing & analysis
Google ecosystem & research
Best for
Versatile proposal support
Writing and editing long proposals
Research and document analysis
Writing quality
Excellent
Excellent
Very good
Long documents
Excellent
Excellent
Excellent
Brainstorming
Excellent
Excellent
Very good
Web research
Excellent
Good
Excellent
Google Workspace integration
Limited
Limited
Excellent
What is ChatGPT?
ChatGPT is OpenAI's general-purpose AI assistant.
It supports a wide variety of tasks including brainstorming, drafting, editing, summarising, analysing documents and generating structured content. Its broad ecosystem, multimodal capabilities and integrated tools make it one of the most versatile assistants available today.
For Horizon Europe proposal writing, ChatGPT is commonly used to generate first drafts, improve clarity, rewrite sections, prepare dissemination plans and explain complex funding requirements.
What is Claude?
Claude is Anthropic's AI assistant with a strong reputation for long-form writing and document analysis.
It performs particularly well when following detailed instructions, maintaining a consistent writing style across long documents and analysing large quantities of text. Many professional writers appreciate its natural tone and ability to preserve structure over lengthy documents.
For collaborative grant proposals that often exceed one hundred pages of working documents, these characteristics can be especially valuable.
What is Gemini?
Gemini is Google's AI assistant.
Its greatest strength lies in its integration with Google Search and Google Workspace, making it particularly attractive for organisations already relying on Gmail, Google Docs, Drive and Sheets. It also performs well on research-heavy tasks that require current information.
For proposal teams working extensively inside Google's ecosystem, Gemini can fit naturally into existing workflows.
Different Product Philosophies
Although all three assistants can help write Horizon Europe proposals, they emphasise different strengths.
ChatGPT aims to be the most versatile assistant. It balances writing, reasoning, brainstorming, research and document analysis within a broad ecosystem of tools and integrations.
Claude prioritises writing quality. It is particularly well suited to reviewing long proposal drafts, maintaining a consistent narrative and following detailed editorial instructions across complex documents.
Gemini places greater emphasis on information retrieval and integration with Google's productivity tools. Teams already working in Google Workspace may find this especially convenient.
Rather than competing on exactly the same strengths, the three assistants have become increasingly specialised.
Feature Comparison
Proposal Drafting
All three assistants can generate proposal content from detailed prompts.
Claude is often praised for producing particularly natural long-form writing, while ChatGPT offers an excellent balance between creativity, structure and versatility. Gemini also performs well but tends to be chosen more for its ecosystem than purely for writing quality.
Winner: ChatGPT and Claude
Editing Existing Proposals
Editing, restructuring and improving existing proposal sections is a major part of Horizon Europe writing.
Claude excels at maintaining consistency throughout long documents and carefully following editing instructions.
Winner: Claude
Brainstorming
Generating project ideas, impact pathways, dissemination activities or exploitation strategies requires creativity as much as technical knowledge.
ChatGPT's versatility makes it particularly effective during these early proposal stages.
Winner: ChatGPT
Research Support
Proposal preparation often requires reviewing background information, state-of-the-art developments and policy context.
Gemini's close integration with Google Search and Google Workspace gives it an advantage for research-intensive workflows.
Winner: Gemini
Working with Long Documents
Large collaborative proposals often involve hundreds of pages of notes, partner contributions and previous submissions.
Claude has developed a particularly strong reputation for handling long documents while maintaining coherence and style.
Winner: Claude
Which AI Assistant Should You Choose?
Choose ChatGPT if you:
- Want one assistant for almost every proposal task.
- Frequently brainstorm new project ideas.
- Need help drafting, rewriting and explaining concepts.
- Value a broad ecosystem of tools.
Choose Claude if you:
- Work extensively on long Horizon Europe proposals.
- Spend significant time editing and refining text.
- Need excellent instruction following.
- Prioritise writing quality and consistency.
Choose Gemini if you:
- Already work in Google Workspace.
- Perform extensive background research.
- Frequently analyse external documents.
- Want close integration with Google's ecosystem.
Final Verdict
There is no single best AI assistant for Horizon Europe grant writing.
ChatGPT offers the broadest balance of capabilities and adapts well to almost every stage of proposal preparation.
Claude stands out for long-form writing, careful editing and maintaining consistency across complex collaborative proposals.
Gemini is particularly attractive for organisations already invested in Google Workspace and for research-heavy workflows.
Many experienced proposal writers now combine several AI assistants, using each where it performs best rather than relying exclusively on a single platform. This increasingly reflects how frontier AI models are being used in professional environments.
Looking for Another Alternative?
If you're looking for software specifically designed for Horizon Europe proposal writing, you may also want to explore Grant Genius.
Unlike general-purpose AI assistants, Grant Genius is built around the proposal itself. It combines collaborative writing with AI-powered assistance tailored to grant development, helping teams draft, improve and review proposals while keeping researchers fully in control of the writing process.