Now it looks like Chrome has a smart Windows installer that combines both approaches. The setup file tries to install Chrome in the Program Files folder and switches to the AppData folder if it fails.
"We did change the download page to install system-level by default (and fall back to user level if that fails or the user says "no" to the UAC prompt). Installing in AppData was never a security measure, it was for convenience to make sure people could install Chrome even without admin rights. Our data shows that *preferring* a system level (Program Files) install with a fallback to user level improves the install success rate," said Mark Larson from Google.
Apparently, this is a feature launched last year, but I haven't noticed it until today, when I had to reinstall Chrome because of this error: "Update failed (error: 7) An error occurred while checking for updates: This computer already has a more recent version of Google Chrome. If the software is not working, please uninstall Google Chrome and try again."
Chrome's help center still recommends to use an alternate installer "to install Google Chrome for all user accounts on a Windows computer. By doing so, you'll replace all other versions of Chrome that may already be installed on your computer for other user accounts." For Mac, "you can install Chrome for all user accounts on your computer if you're signed in as an administrator."