Ruby: Hash#key? vs Set#include?

bench.rb

#!/usr/bin/env ruby
require 'benchmark/ips'
require 'set'

SET = (4..16).to_set.freeze
HASH = SET.each_with_object({}) { |n, ret| ret[n] = true }.freeze

Benchmark.ips do |x|
  x.report('set') { SET.include?(16) }
  x.report('hash') { HASH.key?(16) }
  x.compare!
end

__END__
Result:

  Warming up --------------------------------------
                   set   258.952k i/100ms
                  hash   259.803k i/100ms
  Calculating -------------------------------------
                   set      7.528M (± 3.5%) i/s -     37.807M in   5.028587s
                  hash      8.746M (± 3.8%) i/s -     43.907M in   5.027637s

  Comparison:
                  hash:  8746234.6 i/s
                   set:  7528076.7 i/s - 1.16x  slower
Ruby:

    ruby 2.4.2p198 (2017-09-14 revision 59899) [x86_64-darwin16]

Hardware:

    Hardware Overview:

      Model Name: MacBook Pro
      Model Identifier: MacBookPro12,1
      Processor Name: Intel Core i7
      Processor Speed: 3,1 GHz
      Number of Processors: 1
      Total Number of Cores: 2
      L2 Cache (per Core): 256 KB
      L3 Cache: 4 MB
      Memory: 16 GB
      Boot ROM Version: MBP121.0171.B00
      SMC Version (system): 2.28f7

Software:

    System Software Overview:

      System Version: macOS 10.12.6 (16G1036)
      Kernel Version: Darwin 16.7.0
      Time since boot: 8 days 9:36