Yet Another Related Posts (YARPP) is a great WordPress Plugin that displays a list of related posts and/or pages on your site & feeds based on a unique algorithm. I was using this plugin for a very long time until I came to know about Efficient Related Posts Plugin.
Actually, most of the current related post plugins such as YARPP build the list of related posts on the fly whenever a post or page is loaded which consumes lot of resources, wastes CPU cycles, and ultimately increases your page load time.
Efficient Related Posts Plugin fixes that issue by creating/updating database of related posts only when a post is created/updated.
This means that if the query is slow ( which happens less often), it is the post writer that will have to wait rather than the user.
I started using Efficient Related Posts Plugin few days back and I clearly noticed decrease in page load time on my website.
Now talking about Algorithm, I still feel that YARPP has a much better algorithm than Efficient Related Posts Plugin. But as it can reduce the page load time and speed up your processes, it’s worth giving a try.