WordPress 3.0 comes with a new filter that lets us customize what is used for each permalink structure tag, other than WordPress default.
One of these permalink structure tags is <code>%category%</code>. By default, WordPress always use the category with lowest ID, making <code>%category%</code> impractical for SEO optimization.
Hikari Category Permalink allows post authors to choose among each post’s categories, which of them is used in that post permalink, giving much more flexibility and power to permalinks.
This plugin is a fork of <a href="https://wordpress.org/extend/plugins/scategory-permalink/" rel="ugc">Dmytro’s sCategory Permalink</a>. It has all original features and is compatible with original options, while being more stable and simple, and also fixes 2 recurring bugs.
<h4>Features</h4>
<ul>
<li>You can choose for each post separately, which category is used in its <code>%category%</code> permalink.</li>
<li>Posts without a category set to be used in permalink behave as WordPress default, (which currently is) the one with lowest ID is used</li>
<li>Posts with a category set have it used</li>
<li>In post edit page, where you set the post’s categories, there’s a new feature allowing you to choose which category will be used in permalink</li>
<li>No rewrite rules tweaks are done, making the plugin much simpler and bug free</li>
<li>If you already used sCategory Permalink, you can safely deactivate it and replace by Hikari Category Permalink, all your category permalinks will be used</li>
</ul>

Hikari Category Permalink

For each post, author can choose which category is used in permalink.

John Godley

Provides advanced permalink options that allow you to:
<ul>
<li>Have multiple permalink structures. Permalinks can be assigned to posts or ranges of posts</li>
<li>301 redirect old permalink structures (many structures are allowed)</li>
<li>Category-specific permalinks. Posts in certain categories can be assigned a permalink structure</li>
<li>No need to have a base to the category permalink!</li>
<li>Change author permalinks</li>
<li>Enable periods in permalinks – perfect for migrating old websites</li>
</ul>
All permalinks are real permalinks and do not result in 301 redirections. This means you can change your permalink structure without 
affecting any existing posts and without losing any page rank. Any attempts to access posts in the wrong permalink structure will be 
automatically redirected to the correct URL.
Advanced Permalinks is available in: 
* English 
* Bulgarian (thanks to Alexander Dichev) 
* Belorussian (thanks to Marcis Gasuns) 
* Russian (thanks to Slava Mikheev) 
* Uzbekistan (thanks to Alexandra Bolshova) 
* Lithuanian (thanks to Nata Strazda at Web Hub)
<h4>Example 1: Migrating a permalink structure</h4>
Say you have an existing site with the default WordPress permalink structure <code>/%year%/%monthnum%/%day%/%postname%/</code> and you decide you want to change it 
to a more keyword-heavy <code>/%category%/%postname%/</code>. If you change the permalink setting then all your old posts will be moved, and you will suffer a major loss 
of page rank (not to mention a lot of 404s). With Advanced Permalinks you can define a specific permalink structure for all your old 
posts and then create a new permalink structure for new ones. All your old posts will carry on living at the same URL as before, but all 
new posts will be created using your new structure.
<h4>Example 2: Category-specific permalinks</h4>
Sometimes you want posts in a certain category to appear elsewhere on your site. For example, your usual permalink structure may result in:
/2007/05/02/my-review
However, you want posts in the ‘review’ category to appear as:
/reviews/my-review
Using Advanced Permalinks this is not a problem.
<h3>Documentation</h3>
Full documentation can be found on the <a href="http://urbangiraffe.com/plugins/advanced-permalinks/" rel="nofollow ugc">Advanced Permalinks Page</a> page.

Advanced Permalinks

Allows multiple permalink structures and category-specific permalinks without needing redirects.

Hikari Category Permalink vs Advanced Permalinks