Array#join vs Regexp.union (ran on Ruby 2.0.0)

benchmark.rb

require "benchmark/ips"

input = %w[one two three four five six seven]

Benchmark.ips do |x|
  x.report "Array#join" do
    Regexp.new input.map { |e| Regexp.escape e }.join "|"
  end

  x.report "Regexp.union" do
    Regexp.union input
  end

  x.compare!
end

result.txt

$ ruby -v
ruby 2.0.0p481 (2014-05-08 revision 45883) [universal.x86_64-darwin13]
$ ruby benchmark.rb
Calculating -------------------------------------
          Array#join      4044 i/100ms
        Regexp.union      3947 i/100ms
-------------------------------------------------
          Array#join    46052.1 (±3.6%) i/s -     230508 in   5.012008s
        Regexp.union    43411.7 (±4.0%) i/s -     217085 in   5.009206s

Comparison:
          Array#join:    46052.1 i/s
        Regexp.union:    43411.7 i/s - 1.06x slower