If the NER and the C BSFN do pretty much the same thing the same way, then there probably isn't any appreciable difference in performance.
Having said that, C BSFNs give you the tools to solve a problem using different techniques and design patterns that can make a huge difference in performance. Additionally, C BSFNs allow you to write tighter more organized, manageable and maintainable and reusable code than an NER. And you get to debug the code you write not some mangled, virtually unreadable spaghetti code vomited out by the NER build process.