Engineered Floor Trusses - NOT

Why am I not using engineered floor trusses? It is almost certain that they would be cheaper. These floor-trusses can span several meters, so that the bearer spacing could be 3.6m, and the number of stumps required is a lot less.

I am not convinced that floor-trusses are free form "floor bounce" and "drumming" (resonance) when walked on. I could be wrong about that, but I had more confidence that the traditional stump/bearer/joist approach would keep me happy.