This article is from the Object-Oriented Technology FAQ, by Bob Hathaway rjh@geodesic.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.
[Harmon 93]:
Faster development
Increased Quality
Easier maintenance
Enhanced modifiability
[Booch 94]:
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
 
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