In OS X, is it better to put apps in /Applications or in ~/Applications? I've noticed that pkg installers and obviously apps installed from the App Store) put apps in the /Applications file, yet Steam usually puts them in ~/Applications. Both work, and both are writable by the user, but are there circumstances under which one should be done over the other?
I am the only user of this computer, and shared folders aside, I've disabled guest access.  

(this is coming from a Linux user, so having a root folder be writable seems wrong, unless my permissions are wrong from the start)
What no-one seems to have pointed out so far is that /Applications are usable by everybody &amp; ~/Applications are only for that user.  

Some installers will ask if you want to install for this user or for everybody. That's how it can differentiate.

That will be one of the reasons Steam installs to there, as it's a per user license.

Apple's app licensing, though 'per ID' doesn't prevent all a machine's users from accessing apps purchased under another user account, so everything else usually goes in /Applications by default.

Of course, if you're the machine's sole user, the distinction becomes moot.