Editing Plists - what's the difference?

You are specifying the full path of the command with /usr/bin/defaults. This is more desirable as you might get mixed results with some commands when running in different contexts, like Daemons etc.

You can find the full path of a command by: which defaults or command -v defaults.

@ryan.ball Thanks. I had seem some scripts written with it and some without and couldn't distinguish why. That makes sense.

Using the full path to a command, which is really just a file, is a security measure. This ensures the defaults command you want to run is this one located at /usr/bin/defaults and not this one at ~/Library/.hidden/malicious/keylogger/defaults.