performance comparison of Mongoid, Moped and `mongo` shell w/ MongoDB 2.4.3

mongo_shell.js

function bench(f) {
  var start = new Date();
  f();
  var finish = new Date();
  print( ((finish-start) / 1000) + 's' );
}

bench(function(){
  db.users.find().limit(2000).forEach(function(user){

  });
});

// 2.859s

mongoid_and_moped.rb

require 'benchmark'

num_records = 2000

# Mongoid
puts Benchmark.measure {
  User.limit(num_records).each do |user|

  end
}
#   0.510000   0.070000   0.580000 (  0.665689)

# Moped
puts Benchmark.measure {
  User.collection.find().limit(num_records).each do |user|

  end
}
#   0.480000   0.030000   0.510000 (  0.555456)

Isn't the first one running on the server and the second one has to copy all the data from server to client?

If the first is running in the shell it's copying the data over as well from server to client.