Quick test I've done with some popular frameworks. I wonder if minification affects to parsing speed.

    +--------------------------+---------+---------+---------+--------+
    |         Library          |  Size   | gzip -1 | gzip -9 | brotli |
    +--------------------------+---------+---------+---------+--------+
    | bootstrap.css            |  280813 |   47312 |   33109 |  24533 |
    | bootstrap.min.css        |  232948 |   42003 |   30776 |  22695 |
    | react.development.js     |   87574 |   28733 |   23513 |  19818 |
    | react.development.min.js |   25612 |   10217 |    9224 |   8052 |
    | tailwind-2.2.19.css      | 3642321 |  376787 |  304100 |  82049 |
    | tailwind-2.2.19.min.css  | 2934019 |  354063 |  294632 |  72803 |
    | vue.global.js            |  476920 |  134655 |  105130 |  87121 |
    | vue.global.min.js        |  167898 |   74769 |   65582 |  57922 |
    +--------------------------+---------+---------+---------+--------+

Edit: something important to note: some frameworks (e.g. React) have lots of comments on their un-minified versions, that are removed when minified. That affects their size greatly.

Here's an old article: https://css-tricks.com/the-difference-between-minification-a...

In the example given:

Original - 147 KB

Minified - 123 KB (83%)

Gzipped - 22 KB (15%)

Both - 20KB (14%)

Compression is waaay more effective, so if you have to pick one, go with compressing. Is having readable source code worth the other 2KB? That's up to you. Source maps can do the same thing with less, though. Also, modern devtools have ways of de-minification (if you don't mind all the mangled variable names).

I've seen the same thing with different jQuery versions: https://stackoverflow.com/questions/3239125/is-there-any-poi...

At least with jQuery, it seems that minification matters considerably.