We've tried a couple REST clients over the years, and Insomnia REST Client has won us over the most. Here's what we like about it compared to other contenders in this category:

• Uncluttered UI. Things are only in your face when you need them, and the app is visually organized in an intuitive manner.
• Native Mac app. We wanted the look and feel to be on par with other apps in our OS rather than a web app / Electron app (cough Postman).
• Easy team sync. Other apps have this too, but Insomnia's model best sets the "set and forget" mentality. Syncs are near instant and I'm always assured that I'm working on the latest version of API endpoints. Apps like Paw use a git-based approach to revision history, but I think this actually over-complicates the sync feature. For ensuring I'm always working on the latest version of something, I'd rather have the sync model be closer to Dropbox's than git's, and Insomnia is closer to Dropbox in that regard.

Some features like automatic public-facing documentation aren't supported, but we currently don't have any public APIs, so this didn't matter to us.