Choose Figma if you're part of a design team that needs real-time collaboration and advanced design capabilities. Its robust component system and extensive plugin ecosystem make it perfect for creating polished user interfaces. However, be prepared for potential costs if you have a larger team, and ensure your hardware can handle the load.
Opt for Excalidraw if you value simplicity and need a quick, low-fidelity sketching tool. It's great for brainstorming sessions or for developers sketching out architecture, especially since it's free, open-source, and works offline. However, if you're looking for a tool to create high-fidelity, polished designs, you should look elsewhere, as Excalidraw doesn’t cater to that need.