When comparing Preact vs Inferno, the Slant community recommends Inferno for most people. In the question“What are the best JavaScript libraries for building a UI?” Inferno is ranked 15th while Preact is ranked 16th. The most important reason people chose Inferno is:
Use it however you want in a framework of your own custom design. When things change in the industry, swap things out instead of being locked in by someone else's design.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Lightweight
The size when gzipped is only 3kb, and performance is as good as (or even faster than) React itself.
Pro Same API as react
Avoids having to learn an entire new paradigm, and makes it easy to switch between the two libraries later on.
Pro Lots of examples and libraries
They have a bunch of examples and addon libraries.
Pro Awesome CLI
Preact CLI gives you a perfect scoring PWA out-of-the-box with no configuration.
Pro Modular
Use it however you want in a framework of your own custom design. When things change in the industry, swap things out instead of being locked in by someone else's design.
Pro Pretty light-weight
Inferno weighs in at 9kb gzipped, which is light-weight.
Pro Fast performance
Inferno is one of the fastest UI libraries around and widely considered the fastest.
Pro React compatability
Using the Inferno compatibility package ("inferno-compat"), Inferno can support the vast majority of React codebases.
Cons
Con Difficult to learn
You need to be good in React JS first to learn Preact. Documentation is not rich. And some of the examples given on site are not working. Developers are not much active on Stack Overflow as well.
Con Some React components may not work with Inferno
Inferno and React have different public and private APIs. If 3rd party components use a private API then it's almost certainly going to break when you use it with Inferno.
Once React Fiber is implemented, even libraries that are currently working will break and will not be supported by Inferno.
Con Not very popular
Which can hinder one's opinion of its future, but the future of all "frameworks" is to break things into smaller pieces, so inferno very well might get used by the big names in the future.