The iFly 737 is more efficient than the PMDG NGXu (which struggles in FSX). Users report frame rates between 25-40 FPS at complex airports like FSDT KLAX or FlyTampa OMDB when settings are moderate. Turn down "Scenery Complexity" and "Water Effects" to gain 10 FPS.
If you are looking at , you are likely comparing it to the legendary PMDG. Here is the honest breakdown: