gistfile1.rb

require 'benchmark'

count = 10000

Benchmark.bm do |x|
  x.report { a = []; count.times { a += [1] } }
  x.report { a = []; count.times { a.concat([1]) } }
end

#      user     system      total        real
#  0.230000   0.010000   0.240000 (  0.240109)
#  0.030000   0.000000   0.030000 (  0.029889)