This article is from the Object-Oriented Technology FAQ, by Bob Hathaway email@example.com with numerous contributions by others.
Reuse, quality, an emphasis on modeling the real world (or a "stronger
equivalence" with the RW than other methodologies), a consistent and seamless
OOA/OOD/OOP package, naturalness (our "object concept"), resistance to change,
encapsulation and abstraction (higher cohesion/lower coupling), and etc.
On resistance to change, system objects change infrequently while processes
and procedures (top-down) are frequently changed, providing object-oriented
systems with more resilient system organization.
Exploit power of OOPs
Reuse of software and designs, frameworks
Systems more change resilient, evolvable
Reduced development risks for complex systems, integration spread out
Appeals to human cognition, naturalness