When to use DelegateClass instead of SimpleDelegator?

I am mostly re-posting my question from SO, because i think it can get
lost there, and i hope that on this specialized forum i would get some

So, i do not understand how and when to use Ruby’s DelegateClass
method instead of SimpleDelegator class. All of the following seem to
work mostly identically:

a = SimpleDelegator.new([0])
b = DelegateClass(Array).new([0])
c = DelegateClass(String).new([0])
a << 1
b << 2
c << 3
p a # => [0, 1]
p b # => [0, 2]
p c # => [0, 3]

It does not seem to matter which class is passed to DelegateClass.