Bear with me for some notes that possibly should be in the Nostalgia section, but as I understand it the fan blades of the P&W engines here are hollow, whereas on other 777 engine types they are solid.
If Boeing care to go back 70 years in their archives they will find that the P&W piston-engined Boeing Stratocruiser also offered a choice of propellers, hollow or solid, and that well into the aircraft's life the hollow ones began to give significant problems from internal fatigue and internal corrosion. Eventually, 10 years into the aircraft's operation, an AD was issued that prohibited the hollow units.
AD 58-19-02, if Boeing would care to look it up.
Discussed on a PPRuNe thread here (post #43 in particular) 12 years ago
Propellors on DC6/7, Stratocruiser, Constellation & Britannia - PPRuNe Forums