I installed butterflight on my fleet and I woke up this morning with quads delivering me breakfast in bed! I couldn't find it in the code, but it somehow knew that I like my eggs sunny-side up! Pure magic!
Seriously though, the only difference is in the filtering. BTRF uses fast kalman filters whereas BF uses biquad. I've played around and can't see any noticeable difference other that the fact that BTRF was very easy to set up and flew great with default settings. I also noticed slightly less CPU usage