gistfile1.txt

require 'benchmark/ips'
require 'mail'

Benchmark.ips do |x|
  x.report("'erger@log.com'.split('@')[1]") { 'erger@log.com'.split('@')[1] }
  x.report("Mail::Address.new('erger@log.com').domain") { Mail::Address.new('erger@log.com').domain }

  x.compare!
end

######
Result
######

Calculating -------------------------------------
'erger@log.com'.split('@')[1]
                        77.949k i/100ms
Mail::Address.new('erger@log.com').domain
                         4.756k i/100ms
-------------------------------------------------
'erger@log.com'.split('@')[1]
                          1.842M (± 6.2%) i/s -      9.198M
Mail::Address.new('erger@log.com').domain
                         57.095k (± 9.8%) i/s -    285.360k

Comparison:
'erger@log.com'.split('@')[1]:  1841909.0 i/s
Mail::Address.new('erger@log.com').domain:    57095.3 i/s - 32.26x slower