For me, it's purely personal. I LOVE the fsr's, and sf's, and RF's and VF's. I have fx's and don't get me wrong, they're good motors (even the much maligned 90 fx was good once I sorted it out), but to me they somehow lack character. More to the point I like seeing period engines in period aircraft. To me a curare should have a webra 61, or a 61vf, and a summit, or desire should have hanno, and a typhoon should have a 140rx

"What was so special about an FSR besides in 1974-77 it ran strong in it's heyday?", to me, that's what's special. a bit lame, I know, but them's the brakes.