First off folks: Namor ISN'T faster in terms of flight speed. She can fly at near-lightspeed. She's like Superman. A solar battery. Thus when she goes into outer space she grows exponentially more powerful.
On Earth she can exceed Mach 3.
This is a closer battle than one might think. Starfire and Namor are actually more less equal in experience because A) Starfire is nearly two centuries old 2) Her life has been nothing but warfare and bloody combat since the day she was born. and 3) she's been trained in nearly every form of combat.
However her durability is not nearly as tough as the likes of Namor. High-Caliber weapons can hurt her.
Her strength is VERY undefinable. Sometimes she held her own against Wonder Woman and Captain Marvel. Other times she had trouble with the likes of Slade and Beast Boy. However based on her best performances she's definitely in the lower class 100s