https://old.reddit.com/r/ruby/comments/f26g8h

result

$ ruby -v t.rb
ruby 2.6.5p114 (2019-10-01 revision 67812) [x86_64-darwin19]
Warming up --------------------------------------
             if else   186.397k i/100ms
case with comparison   149.445k i/100ms
      case all range   127.260k i/100ms
     case hash cheat   190.074k i/100ms
Calculating -------------------------------------
             if else      3.447M (± 7.5%) i/s -     17.149M in   5.007151s
case with comparison      2.388M (±18.2%) i/s -     11.657M in   5.065894s
      case all range      2.416M (±11.9%) i/s -     11.962M in   5.045475s
     case hash cheat      4.460M (±14.9%) i/s -     21.668M in   5.005362s
 

t.rb

require 'benchmark/ips'

Benchmark.ips do |bm|
  bm.report 'if else' do
    x = rand(1..20)

    if (1..5) === x
      "It's between 1 and 5"
    elsif x == 6
      "It's 6"
    elsif x > 10
      "It's above 10"
    else
      "It's probably 7, 8 or 9"
    end
  end

  bm.report 'case with comparison' do
    x = rand(1..20)
    case x
    when 1..5
      "It's between 1 and 5"
    when 6
      "It's 6"
    when x>10
      "It's above 10"
    else
      "It's probably 7, 8 or 9"
    end
  end

  bm.report 'case all range' do
    x = rand(1..20)
    case x
    when 1..5
      "It's between 1 and 5"
    when 6
      "It's 6"
    when 7..9
      "It's probably 7, 8 or 9"
    else
      "It's above 10"
    end
  end

  bm.report 'case hash cheat' do
    x = rand(1..20)
    case x
    when 1, 2, 3, 4, 5
      "It's between 1 and 5"
    when 6
      "It's 6"
    when 7, 8, 9
      "It's probably 7, 8 or 9"
    else
      "It's above 10"
    end
  end
end