Ionicons is an open-source service that provides a huge number of icons to developers. It is designed to serve as a cross-platform hybrid and web app framework. It is available for use on Android and iOS smartphones, and desktop applications. 

It is preferred by developers for its easy-to-use and simple features. It doesn’t require installation as it is packaged by default. It provides scope for the customization of icons as well. It also offers variants and is recognized for its platform specificity. It enables users to use size attributes, specify icon colors and adjust stroke weight to create the right appearance.

sIFR is a JavaScript and Adobe Flash dynamic web font implementation.

Comparison Ionicons vs sIFR