Never delete a web page. You may redesign new layout, you may build new stronger engine, but never delete a good old web page. Old information can always be good information. It must be having some value for some user. This is where archiving came in handy.
You must keep your old web page alive because several things. First, people may bookmark your page, either at their on browser or online bookmark. They will absolutely get disappointed if they realized that their favorite page is gone. Not only people, other site may have link to your page. You remove the page, the link will be dead. People who click the link will not be happy, and so does the site owner. Never expect them to link your page again after you gave them that bad experience.
One more side that will be unhappy if you’re removing pages. One big side actually. Yes, the search engine. Search engine are quick in indexing pages but slow in updating their database. So your page will still be listed in the result, but once people click it, another bad experience happen.
That is why any pages you ever publish to the world must remain alive forever. The URL must be kept valid. It doesn’t cost more than creating a new content, but it could help attract people to always come back to our site.