Sorry - couldn't help myself for a minute, there
.
I think that both of you are right - both GUIs and command lines have their place.
If you want to carry our repetitive tasks, or a task on a group of files, a CLI is very useful.
If you only use a tool occasionally, though, a GUI where you select options for a dialog box is much easier to use than having to memorise cryptic parameters.
Both have their place. Both are useful.