This is a plugin I found recently and really enjoy. It gives you the opportunity to redirect several webpages to alternatives. For example Youtube to FreeTube or Piped. If I search for youtube in Firefox, FreeTube automatically opens and shows me my feed. I like it, I use it, I can recommend it.
It’s like comparing apples to oranges, both are fruit but very different. LibRedirect has a nicer UI than Redirector and also has content discovery mechanisms for each of the supported sites as well as the ability to ping each instance and TOR support.
Redirector is just an extension that takes URI, passes them through a REGEX find/replace and then sends the user to said new URL.
I say it’s comparing apples to sliced apples with a slicer. Minus the performing redirection part, LibRedirect is a more polished ruleset generator for redirection extensions.