The key difference is that Object#type is deprecated. From the RDoc for Object#type:
Deprecated synonym for Object#class.
Here’s why you should use Object#class:
Returns the class of obj, now
preferred over Object#type, as an
object‘s type in Ruby is only loosely
tied to that object‘s class. This
method must always be called with an
explicit receiver, as class is also a
reserved word in Ruby.
In reality, you probably want to use Object#respond_to? instead of checking for the class of an object in most cases.