If you're looking for a charming, low-fidelity tool for quick brainstorming or sketching architectural ideas, Excalidraw is your go-to. Its hand-drawn aesthetic is perfect for informal sessions, and being free and open-source adds tremendous value, especially if you prefer keeping data local or need it to work offline. However, avoid Excalidraw if you require high-fidelity visuals or a full suite of design tools, as it lacks the polish and depth found in commercial software.
On the other hand, if you need a robust solution for organizing personal notes or managing projects, Obsidian stands out with its powerful customization options and local data storage for enhanced privacy. It’s ideal for building a private knowledge base but might not suit those who favor cloud-based systems or need real-time collaboration. If you're willing to navigate its learning curve, Obsidian offers significant flexibility, making it the better choice for personal organization over Excalidraw.