301-redirects are one extra step between the source and the destination page. Aside from adding unnecessary weight to the site, and an extra second of waiting for the user, 301 redirects also dilute PageRank.
How does PageRank Work?
Essentially, how PageRank works is that a page passes some of its authority to all pages it links out to – whether internal or external. Those pages pass on some of that authority from the first page further to other pages they link out to – albeit diluted. Level 3 pages still pass on some of that authority to level 4 pages, but it’s even more diluted than the authority passed on by level 2 pages, and so on.
In that sense, PageRank can almost be seen as a gradient, and every single in-link, while still connected to the source and still gaining benefits from its authority, receives less authority from the source page than the page superior to it in the in-link chain:
Redirects take the place of what would otherwise be a 200 URL. They tell search engines “this link was removed, so we’re taking you to the next best page”. In that sense, while 301 redirects, unlike 404-errors, still pass on authority – the authority is diluted for every redirect that exists.
In the example above, if internal links had 301 redirects, the same level of authority from the source page would only be passed down to pages at the 2nd level. Essentially, the potential to pass on more authority to more internal pages is wasted. Again, this is OK in situations where the original content was removed – but should be avoided in scenarios where other workarounds are possible: