yum localdowngrade option?

[Andre Robatino]

In testing a new version of a package, I'd like to be able to switch
between older and newer versions without having to repeatedly download
either one.  Yum can update using local RPMs with the localupdate
option, but I don't see anything like a localdowngrade option.  Is there
another way to do this (other than erase and localinstall)?  I'm asking
because

http://illiterat.livejournal.com/7834.html

claims that "there are no known reasons to use rpm instead of yum".