The total number of classes decreases

Repeated code

Hollywood Principle: don't call us we call you

Interface segregation principle

The strategy principle

Strive for loosely coupled designs

The multi-tasking principle

Factory Method encapsulates instantiation and Abstract Factory does not.

The abstract factory allows to encapsulate the instantiation of families of related classes.

Abstract Factory is not considered officially a pattern.

The factory method is a method and the abstract factory is an object. 

The Factory Method uses inheritance while the Abstract Factory uses delegation.

A decorator must be a subclass of the concrete component it wraps.

Decorators have the same supertype as the object they decorate.

A decorator maintains a reference to the component object it wraps.

A decorator adds its own behaviour before and/or after delegating to the object it decorates.

Objects can be decorated at runtime (with as many decorators as desired).