bench.rb

# frozen_string_literal: true
require 'benchmark/ips'

Benchmark.ips do |x|
  x.report('+@') { +"" }
  x.report('dup') { "".dup }
  x.compare!
end

result.txt

Warming up --------------------------------------
                  +@   436.074k i/100ms
                 dup   292.061k i/100ms
Calculating -------------------------------------
                  +@     11.490M (± 1.9%) i/s -     57.562M in   5.011607s
                 dup      5.121M (± 1.7%) i/s -     25.701M in   5.020415s

Comparison:
                  +@: 11490470.9 i/s
                 dup:  5121009.0 i/s - 2.24x  slower