Tools like Flagr typically function as a microservice that handles all of the feature evaluation. That means you need a network request every time you want to get a feature's value. With GrowthBook, there's a single cacheable JSON definition of all of the features and then evaluation happens locally within the SDKs. We found this approach to be much better for performance and scalability.

The other missing part in most feature flagging tools is the analysis side. Most tools let you run an A/B test, but it's up to you to track the data, process it, and run it through a stats engine. We built that part directly into GrowthBook.