Comparison of Node Pager modules

Entity Pager

Concept: Entity Pager module is easy to use, allowing you to create new Navigation blocks in a few seconds. It provides next and previous navigation on any Entity (e.g. Nodes, Users etc..).
The items and the order they appear are completely customizable via Views. Using the module you can add multiple different navigation blocks on the same entity. It runs fast with the minimum of processing and will happily provide navigation on 50,000 nodes in a fraction of a second. For more complex pagers, it can combine with the Entity Reference module to create sub-navigation.
Documentation: Good - it comes with an example and also a YouTube training video.
Drupal 7: Stable-version Available
Drupal 8: Alpha-version Available

Custom Pagers

Concept: Custom Pagers allows administrators to define context-sensitive previous/next pagers for any node type. The list of nodes to be cycled through is generated by a user-selectable view, and each pager can be displayed above or below the node body or in a sidebar block. This makes it possible to duplicate the paging functions of forum.module and book.module, as well as more complex stuff like comic strip navigation. Requires token.module and views.module.
Drupal 7: Dev-version Available
Drupal 8: Not Available

Flippy

Concept: Flippy is an ultra-simple module that generates previous/next pagers for content types. On the Node type administration screen, you can turn Flippy on or off
for each content type. It'll generate a unique pager for each content type, so you can page through Articles or page through Blog posts, but you can't page
through all nodes on the site.
Drupal 7: Stable-version Available
Drupal 8: Dev-version Available

Previous/Next API

Concept: This module allows you to know the previous or next nodes for any given node. This is very useful for providing navigational links to the user without the expensive queries required to dynamically deduce such information on the fly.
Drupal 7: Dev-version Available
Drupal 8: Dev-version Available

Comparison after trying each:

Each of these modules has taken a fundamentally different approach to solving (coding) the problem.

• Previous/Next API it is an API and does not provide any UI.
• Entity Pager simple with advanced features, create flexible navigation in few seconds via Views, place them on screen via Blocks, fast, works on 10,000's of nodes in a fraction of a second.
• Flippy no flexiblity, it only allows you to navigation through a whole content type.
• Custom Pagers it is node based (not entity based) and uses PHP snippets.