Preact build is 68% smaller than React with a two lines changes

While I do appreciate preact, and have used it... it doesn't contain all the error detection and messaging that react proper does... that's where a lot of that much smaller initial load comes from. When you aren't having issues it's great... if you are, less so.

It really depends on your needs, you can get a very small app/module via preact, and I like it a lot. If you're building for a larger environment, or larger applications, you may be better off eating the extra 60-80k or so for React proper.