Using if statement in index.php instead of creating separate template files

Before I start, it will be a good idea to check out my answer to the following post

It will give you some more insight

As I stated in the linked answer, You can have a fully functional website with just index.php as template to display posts with for all pages

What you are doing is fine, and if there are any speed difference, it should be very very minute. I would however stress that your approach might have the drawback of one templates having to do to much.

Because you would want to do things differently for different pages, it will be a good idea to create those templates needed the relevant page loads. As I said, if there is any speed difference with any method, it would be really very very minute which you will not worry about. Having different templates for different pages with different layouts do have the advantage of that you do not overload one template with a lot of unnecessary code.

For extra reference, see my answer to the following post as well

Related Posts:

  1. How to search for categories and/or tags?
  2. Sticky posts on home page, search, tag and archives without plugin
  3. Different templates for parent and children categories/taxonomies
  4. Create product category and keyword search form in woocommerce? [closed]
  5. Custom Query to search through categories
  6. Exclude a category from the filed under list only on some templates
  7. Create single.php for specific category by category id
  8. How to show empty category in admin menus search
  9. How to select product category while adding new product in woocommerce? [closed]
  10. How do I get the total number of categories in a list of search results?
  11. Search by word, category, tag, author
  12. Filtering search results
  13. How to override Category rendering mechanism
  14. How to control template resolution if both Author and Category filter in place?
  15. Custom page for WooCommerce’s /product-category/
  16. Code to pull in a PHP file named after the category ID
  17. Exclude category from Tag Template
  18. Multiple Category Search
  19. How to make a Thumbnails Mosaic
  20. Are Category or Tag Archive Pages Possible?
  21. get_the_category and echo out link to child-most/deepest category
  22. Possible to make a subdirectory that loops through a single category?
  23. Need Category RSS Feed that shows all posts
  24. WooCommerce IF statements not working
  25. I need to create a search form that will display search results from specific category
  26. Set a them for all subset of category
  27. Search Posts / Pages with multiple options?
  28. How to display only posts assigned to a particular, isolated, subcategory
  29. How to query post like normal search would do. within search.php page
  30. Archive.php filtered by pre-determined category
  31. one category template for multiple categories
  32. WordPress search only showing a few posts
  33. The default code for “posts_nav_link” on category.php isn’t working
  34. Only one post is showing on category page, why?
  35. Select posts by name and category per REST API
  36. How do I toggle pagination on/off in search results and category listings via a link?
  37. Updating category template to change how subcategories display
  38. Categories overview that links to page displaying posts
  39. How can I get categories IDs if multiple categories requested via URI?
  40. Refine/Filter the Search Results by Category
  41. Category template to show different categories based on parent
  42. Does “show_option_all” in wp_list_categories do anything?
  43. How can I improve this taxonomy treating approach?
  44. Show matching categories in search page
  45. How to insert category list into post creation page, and retrieve chosen categories?
  46. Keyword search in multiple categories
  47. Limit number of posts on a custom category template – breaking pagination
  48. WordPress Custom Search Form Displaying Unexpected Results
  49. Get URL Category Name By ID
  50. Custom template for sub-sub-categories
  51. What Must to Display the “mysite.com/category” URL?
  52. Group search results by category
  53. Woocommerce search form with category select
  54. How to use wp_list_categories with plugin category?
  55. Why is my sub-category template showing the wrong posts
  56. Add Date & Author Meta to Category Archive Page
  57. Display subcategories selectbox on each category page
  58. Search form options group categories
  59. Category link redirect to custom template page instead of index.php?
  60. I would like to feature a tip on the homepage
  61. How can I include custom category and tag base in template files?
  62. Different header for each category
  63. Category Template – Show Last Entry as Featured
  64. Custom post type archive category page results in 404
  65. Include home page template in specific category template
  66. Output Title of Post’s Current Category
  67. Showing different posts on category pages
  68. Displaying categories in different template problem
  69. Include last post date in get_categories loop
  70. WordPress Default Category and Custom Taxonomy Selected Attribute not Working After Searched in wp_dropdown_categories Array
  71. Automatically adding tags and categories into Post Excerpt for searching
  72. How to list posts from a sub-category that is listed in a parent category (more details below)?
  73. Return all Tags and Categories in Separate List
  74. Search by tag, category and author without plugin
  75. Adding a category view to a page
  76. Using a template page parent breaks page
  77. Issue with WordPress category search
  78. get_terms sort order with child categories of varying depth
  79. the_content() not showing full posts in category template
  80. Use different file includes for single.php
  81. Display Taxonomies in loop with template args
  82. 404 error when i try to search by category or by tag
  83. Choosing different templates for categories
  84. Show posts from all categories
  85. Make related posts display first in search result
  86. A search box for all sites – Multisite
  87. Getting page/category content to show up in my custom page template
  88. One category not displaying template updates
  89. Several loop in search result
  90. WordPress a template for subcategories fo a given category, but not for root category
  91. Custom Fields to Category edit page, then displaying them in a template correctly
  92. Template files not working for archives and categories
  93. Query posts that have all the specified tags
  94. 2 Categories using same template but one has a problem? [closed]
  95. Display category tree of a post in search results
  96. Why does my category page display “posted on…” when all I want it to do is display categories?
  97. How to create a template for categories
  98. How to load/include category templates based on conditionals?
  99. Remove “All categories” from searchbar dropdown
  100. Display different sidebar based on search results from one category