Thermo-chemical scalar probability density functions (pdfs) measured in nonpremixed hydrogen and methane turbulent jet flames are compared a priori with an advanced conventional assumed shape pdf model, as well as a recently proposed constructed pdf model. The constructed pdf, by incorporating the underlying physics of advection by all unsteady eddies, molecular diffusion and chemical reaction, displays consistent and substantial a priori improvement over the conventional assumed shape pdf. In addition, the constructed pdf model may be parameterized by considerably fewer lower moments, and in particular, first moments, promising affordable and accurate implementation in a moment-equation solver.