If you’re a developer or product team looking to create polished prototypes or need a canvas for real-time collaboration, tldraw is your best choice. Its "make real" feature turns sketches into functional UI, which is great for more structured design projects. However, keep in mind that commercial use requires a paid license.
On the other hand, if you're after a casual sketching tool for brainstorming with a charming hand-drawn style, Excalidraw is ideal. Its open-source nature allows for self-hosting and offline use, making it versatile for quick sketches and architecture layouts. Just be aware that it's not suited for high-fidelity visuals or extensive design projects.