Why custom services perform better than services module

I have created custom services module which gives json output and I created a resource using services hook_services_resources().

The custom ones gives response in 200ms where as services module gives in 4sec.

What is the reason? Does it take lot of time for formatting?authentication?access checks?

Steps to reproduce-
Custom way--
1)Install drupal
2)Create a content-type of complicated nested field collections
3)create a menu in custom module
4)output of that menu is drupal_json_output of the node data.

Services way---

1)Install drupal
2)Create a content-type of complicated nested field collections

3)install services module and create own module for services which will retrieve that node(along with field collection data) using hook_services_resources