It seems like both of these gems perform very similar tasks. Can anyone give examples of where one gem would be more useful than the other? I don't have specific code that I'm referring to, I'm more wondering about general use cases for each gem. I know this is a short question, I will fill in the blanks upon request. Thanks.
The reason they look like they perform similar tasks is OpenURI is a wrapper for Net::HTTP, Net::HTTPS, and Net::FTP.
Usually, unless you feel you need a lower level interface, using OpenURI is better as you can get by with less code. Using OpenURI you can open a URL/URI and treat it as a file.
See: http://www.ruby-doc.org/stdlib-1.9.3/libdoc/open-uri/rdoc/OpenURI.html and http://ruby-doc.org/stdlib-1.9.3//libdoc/net/http/rdoc/Net.html
I just found out that open does follow redirections, while Net::HTTP doesn't, which is an important difference.
For example, open('http://www.stackoverflow.com') { |content| puts content.read } will display the proper HTML after following the redirection, while Net::HTTP.get(URI('http://www.stackoverflow.com')) will show the redirection message and 302 status code.
来源：https://stackoverflow.com/questions/16764030/what-is-the-difference-between-rubys-open-uri-and-nethttp-gems