test.rb

require 'active_record'
require 'benchmark/ips'

ActiveRecord::Base.establish_connection(
  :adapter => 'sqlite3',
  :database => ':memory:')

ActiveRecord::Base.connection.create_table('posts') do |t|
  t.string :name
  t.timestamps
end

class Post < ActiveRecord::Base
end

post = Post.create(:name => 'aaron')
id   = post.id

Benchmark.ips do |x|
  x.report("new")      { Post.new }
  x.report("new args") { Post.new(:name => 'aaron') }
  x.report("create")   { Post.create(:name => 'aaron') }
  x.report("find")     { Post.find(id) }
end

__END__
3-2-stable:

Calculating -------------------------------------
                 new      1597 i/100ms
            new args       755 i/100ms
              create        91 i/100ms
                find       193 i/100ms
-------------------------------------------------
                 new    24843.5 (±8.8%) i/s -     124566 in   5.056542s
            new args     9188.9 (±9.5%) i/s -      45300 in   4.998662s
              create      932.8 (±7.3%) i/s -       4641 in   5.002245s
                find     2066.4 (±5.5%) i/s -      10422 in   5.058268s
master:

Calculating -------------------------------------
                 new      2104 i/100ms
            new args       871 i/100ms
              create        95 i/100ms
                find       213 i/100ms
-------------------------------------------------
                 new    33856.6 (±7.9%) i/s -     168320 in   5.005236s
            new args    10681.3 (±7.3%) i/s -      53131 in   5.002680s
              create      970.3 (±7.0%) i/s -       4845 in   5.019001s
                find     2207.7 (±7.2%) i/s -      11076 in   5.042719s

❤️