What's the core feature compared to https://www.alphaxiv.org/ https://www.alphaxiv.org/, https://www.semanticscholar.org/ https://www.semanticscholar.org/ and j

What's the core feature compared to https://www.alphaxiv.org/ https://www.alphaxiv.org/, https://www.semanticscholar.org/ https://www.semanticscholar.org/ and just using Gemini? I feel like there are many research assistants but not sure which one is the best