Now, old Reddit is only visible while logged in.
Old Reddit was better overall because it was more utilitarian and lightweight. There was much more information density. It also loaded faster. No
stupid splash screens or loading animations, it got straight to the content.
It was also friendlier to legacy browsers and systems because you could browse it without JavaScript. The post list is split into pages instead of bottomless scrolling. The new Reddit obviously requires a recent version of JavaScript. Without it, bottomless scrolling is broken.
Most importantly, old.reddit.com was friendlier to web archival. Much more information on one page. 25 posts are listed on a page, and up to 200 comments on a post page (up to 500 with the limit=500 URL parameter) could be archived at once.
URL-based pagination would also allow archiving lists of older posts. Wayback captures of the new Reddit only list up to
three posts and there is no URL-based pagination, so the post history can not be archived.
However, new Reddit (and Reddit's 2018 layout) has the benefit that it previews the text content of text posts. You don't have to press a button to be able to read the text, but it already appears on the page.
i.reddit.com, which was shut down in 2023, had a major benefit for web archival: The text content of text posts was included as a hidden section in the HTML document that was revealed when the "expand" button was pressed, while old.reddit.com only loaded it in the moment the "exapnd" button was pressed. The former is also how voat.co (Reddit-style site, shut down in 2020) did it.
Take this archived web page for example:
https://web.archive.org/web/20130419191 ... /AskReddit
If you click one of the "Aa" buttons on the page to expand the text content, it immediately opens the text because nothing is loaded from the server but it already is part of the HTML document. If it weren't, it wouldn't have been archived.