bm.rb

require 'benchmark'

s1 = Struct.new(:login, :password).new("login", "password")

class S
 attr_accessor :login, :password
 def initialize(login, password)
   @login    = login
   @password = password
 end
end

s2 = S.new("login", "password")

times = 100_000_000

Benchmark.bmbm do |b|
  b.report("Struct") do
    times.times do
      s1.login
      s1.password
    end
  end

  b.report("attr") do
    times.times do
      s2.login
      s2.password
    end
  end
end

output.txt

Rehearsal ------------------------------------------
Struct  12.930000   0.000000  12.930000 ( 12.943928)
attr    10.280000   0.000000  10.280000 ( 10.276997)
-------------------------------- total: 23.210000sec

             user     system      total        real
Struct  12.850000   0.000000  12.850000 ( 12.858140)
attr    10.330000   0.000000  10.330000 ( 10.335870)