difference between querying database and using the loop

There is no absolute better/worse/best/worst implementation. The correct implementation depends on what you’re trying to accomplish.

For a great explanation, I direct you to this post by Digging Into WordPress, which explains the 4 basic means of interacting with the WordPress Loop:

  • Default Loop

    So what makes it “default”? Mostly because it uses the default query to loop through post content, making it the loop used like 99% of the time for most themes. It tells WordPress to loop through posts and display the information according to context

  • Loop with query_posts()

    The query_posts function enables us to modify the [default] query and display our desired results. We can either override the entire query or keep it around and just change a few parameters.

  • Loop with WP_Query()

    Use WP_Query for creating multiple, customized loops. By setting up additional instances of WP_Query in your theme, you can create any number of multiple loops, and customize the output of each.

  • Loop with get_posts()

    Use the get_posts() function to easily create additional, static loops anywhere in your theme. get_posts accepts the same parameters as query_posts, and is perfect for adding static, custom loops to your sidebar, footer, or anywhere else.

Give that post a read; it will help you understand when/how to use each option.

EDIT

p.s. more from Digging Into WordPress: if you use one of these methods to modify the query, you will want to familiarize yourself with when/how to reset the query.

Related Posts:

  1. Some doubts about how the main query and the custom query works in this custom theme?
  2. Using a custom WP_Query with get_template_part loop
  3. Loop within a loop?
  4. How to list some posts first in the loop based on post id
  5. Display posts the match taxonomy term linked from wp_list_categoies?
  6. WordPress Custom Query to show posts from last x years
  7. How to order posts tag by tag?
  8. Loop through all tags & output posts in alphabetical list
  9. Pagination with 5 posts per page
  10. Merging a complex query with post_rewind and splitting posts into two columns
  11. Pagination Not working on Home Page with 2 Query
  12. meta_query not working properly
  13. Exclude post on loop by multiple meta key value
  14. Sort by meta key on archive page
  15. How to display 3 different loops in 3 columns on homepage
  16. Splitting the main query in multiple loops with query_posts and/or pre_get_posts?
  17. Query sticky posts with thumbnails
  18. Show all parents and children in custom post type in right order
  19. Why is this coming back as null? Thats wrong. There is one post
  20. Ignore post by meta value in the main query
  21. How to retrieve current page WP_Query arguments?
  22. WP_Query doesn’t get sticky post at the top, when used in a page template
  23. How to limit WP_Query to one result on the loop?
  24. Prevent duplicate post from dynamic multiple loops
  25. if/else on custom query gives 200 OK when condition not met?
  26. Multiple Loops Inside a Function
  27. Sticky posts are not showing at the top of category posts
  28. Random loop with code to prevent duplicate output returns no output at all from time to time
  29. How to use offset in WP_Query
  30. Multiple loops without repeating content
  31. Can I set my WP_Query to be a Main Query?
  32. Group and list posts by custom taxonomy
  33. Show scheduled posts in main loop but not in WP_Query?
  34. Filtering posts from different categories into different section by doing WP_Query only once
  35. How to make search for posts using get method?
  36. How to get list of posts from permalinks?
  37. Custom taxonomy.php not working
  38. different for loop if screen resolution < 1000px
  39. Transient api Caches confused
  40. how to use pre_gets_posts to exclude one queried ID from homepage loop
  41. sort and display posts by custom field (wp-query and the loop))
  42. WP_Query – Adding “offset” posts to the end of the loop
  43. Conditional operator OR not working with custom fields
  44. Get posts that do not have the same tags as current
  45. wp_query is showing posts from other categories
  46. Should I reset $wp_query?
  47. Exclude a Woocommerce product from WP_Query
  48. WP_QUERY wrong ammount of posts
  49. How to add sort order to incremented and paginated category loop
  50. How does WP generate the default $query in WP_Query based on the URL?
  51. How to remove only the latest sticky post from the loop
  52. Expecting statement error from php loop using ACF plugin
  53. How I can repeat 2 HTML templates in a WordPress Query?
  54. How do I sort this custom list of sticky posts
  55. Query only displays one page_id
  56. Get posts with no tags?
  57. wp-query, pull children of parent page
  58. I am officially missing something about transient posts
  59. Offset WP_Query by negative 1
  60. WP_Query orderby random do not repeat infinite scroll – one loop
  61. How do I get the content of a custom instance of WP_Query?
  62. $post in wp_query?
  63. How to pass the current content of $wp_query to a new page?
  64. How can I have sticky posts while ALSO showing posts from a specific category using one WP_Query?
  65. ACF: How can I publish values of ACF fields in a loop while using wp_query?
  66. Can I alter the main loop to ‘orderby’ a custom callback?
  67. Show a message if there are no active posts in category
  68. WooCommerce | AJAX | Product Pagination | Help me implement Ajax Pagination
  69. Problem with my loops
  70. Regarding a custom loop and output HTML tags
  71. What’s causing an infinite loop?
  72. display the children of the post using the current page as the main parent
  73. Display 3 levels of categories on page
  74. Paging works correctly on local version, but not live?
  75. pages shortcode filtering by category
  76. Custom post type loop error: Trying to get property of non-object
  77. Second WP_Query loop shows data from main query
  78. Meta Query if Values Don’t Exist
  79. Get post Number with local loop and template
  80. How to add in WP_Query to every 3 posts displayed? [duplicate]
  81. Display three sequential posts on each page load, without repeating previous
  82. display post multiple times based on array of dates
  83. How to make a wordpress loop file that displays posts based on certain conditions
  84. Problems with WP_Query, Loop, a condition and Posts per Page
  85. WP_Query secondary query failing
  86. Custom loop – Isolating post meta output depending on current query taxonomy terms
  87. Issue in If else condition [closed]
  88. Pagination not working with WP_QUERY
  89. Sorting is not working in WordPress WP_Query
  90. Add custom WP_Query after the first 3 posts
  91. How do I display posts with specific value in a custom field into my loop?
  92. Order by multiple meta keys on wordpress
  93. wp_query pagination links producing 404
  94. Display First posts without the default featured image
  95. Pagination problem with multiple loops on the same page
  96. Can’t seem to get an else statement correct? [closed]
  97. Output ACF field dynamicaly within a taxonomy loop [closed]
  98. How do I split a large query with a semi-expensive function included into multiple smaller queries
  99. Query All Posts: Either Display Most Recent or One with Particular ACF Value Chosen
  100. after refresh the id that shows correct in first time click, changes to 1