Why it is the best

I looked into the JS and CSS files that were generated by autoptimize and understood that it was the best JS/CSS plugin to merge JS/CSS files.
It generates the filename only once and it is a great thing. If you press the delete cache button, it will sure delete the previous files but it creates new files with the same filename.
It is super important for GoogleBot.
When Googlebot stores a page in the cache, it only stores the HTML. It does not store the CSS files nad the JS files to save space on the Google servers.
So everytime, you or googlebot visits its cache it calls the HTML file on its server and then it calls the JS/CSS files on your server (remember they aren’t stored). The other JS/CSS plugins contanstly change the name of CSS/JS files, so that it creates a 404 error.

Let me explain:

Googlebot partially crawls your page. Sometimes, they crawl the HTML, sometimes the images, sometimes the CSS and sometimes the JS files. So, if Googlebot crawls the HTML and if the JS/CSS file names have changed it would return a 404 error page
It does not happen with autoptimize because autoptimize does not constantly regenerate the CSS/JS filenames. With autoptimize, Googlebot will always find the right JS/CSS filenames even if you deleted the cache.