Sorry, but I have to agree. I'm a big noctua fan and use 4 of them of them in my gaming rig myself, and ive been experimenting with lots of different brands of fans over the last month.......
There's just no way in the world you'd see a 27 degree drop, at the same RPM, unless you'd moved your entire room into a freezer. In fact at any rpm you wouldn't see that percentage drop, unless your previous fans were barely moving or faulty. You've missed something somewhere in your measurements or testing strategy bud, sorry.