If you are in a position where you want to remove the colossus that is Xcode, here is the terminal command to use.
sudo /Developer/Library/uninstall-devtools –mode=all
In my case, I was using migration assistant to migrate my applications and user account to a new laptop. My older laptop had an older version of Xcode that I didn’t want included in the migration and as it is so big, I didn’t want to take the chance.
magp.ie 
Xcode generally seems to pick up the right version, but some people have reported that it still uses the old version in /usr/local/bin. If you’re not using an older version of Xcode, you can safely delete the one in /usr/local/bin.