alias vs alias_method when used for class methods in ruby

alias.rb

# http://blog.bigbinary.com/2012/01/08/alias-vs-alias-method.html

class X
 class << self
   def skip
     alias :scenario :skip_scenario
   end

   def scenario
     puts "scenario"
   end

   def skip_scenario
     puts "skipped scenario"
   end
 end
end

class Y < X
 skip
end

class Z < X
end

X.scenario
Y.scenario
Z.scenario

alias_method.rb

class X
 class << self
   def skip
     singleton_class.class_eval { alias_method :scenario, :skip_scenario }
   end

   def scenario
     puts "scenario"
   end

   def skip_scenario
     puts "skipped scenario"
   end
 end
end

class Y < X
 skip
end

class Z < X
end

X.scenario
Y.scenario
Z.scenario