- archive.org - lots of stuff was never archived, or is not available due to /robots.txt
- ctrl-S - not self-contained, compatibility depends on which browser you use (Safari at least gets it right and puts it in a single file, but then other browsers can't open it. Firefox usually saves it correctly and portably, but now you have multiple files, and you can't rename them because they have references to each other, which makes it hard to organize. Then there's all the JavaScript that web pages sometimes have, which can break in the archive.)
If a PDF is available it's easily better than these alternatives. In general I save webpages I really want to refer to later by copy-pasting the text out and manually reformatting as Markdown, or sometimes with wget.