Appending to a string vs stringIO

gistfile1.rb

require 'rubygems'
require 'benchmark'
require 'stringio'

Benchmark.bm do |x|
  n = 1000000
  x.report('string') do
    string = ''
    appended = 'b' * 100
    
    n.times { string << appended }
  end
  
  x.report('stringio') do
    string = StringIO.new
    appended = 'b' * 100
    
    n.times { string << appended }
  end
end

#       user     system      total        real
# string  0.360000   0.090000   0.450000 (  0.441618)
# stringio  0.440000   0.100000   0.540000 (  0.544054)