If you're an API developer looking for a straightforward, cost-free solution, choose Hoppscotch. Its open-source nature and offline capabilities make it a solid choice for individual projects or small teams that prioritize flexibility without advanced integrations. However, if you need extensive third-party connectors or more sophisticated functionality, Hoppscotch may not meet your needs.
On the other hand, if you're focused on personal organization and wish to maintain a private knowledge base, Obsidian is your best bet. Its extensive customizability and Markdown support cater to users who want to create a tailored experience. However, be prepared for a learning curve, and keep in mind that it’s not ideal for real-time collaboration or those seeking cloud-based storage options.