What should I use more in Autodesk AutoCAD - command line or GUI and why?

For beginer it is good to use "GUI" because it moor simple and you don't need to remember the short of command word But for the pro use the command line is moor faster and make the worke moor confort

For me, I'm using command line more, as I'm familiar with it especially I'm using my own shortcut long ago, but sometimes I use GUI for commands which I rarely use.
Moreover You can add your own shortcuts for most used commands by overriding the default shortcuts, it’ll save much time, but it should be your own cause no one else can recognize for your shortcuts.
We should use all features in AutoCAD, "especially the new ones" like Ribbon, it's giving more support, and it depends on the way that the user will save time and effort to achieve the task.

Using the command prompt or icon menu has always been a personal preference, beginners operators they tend to stick with icons.
However knowing the command input structure, has it’s advantages.
For example if you know a command and how it works and you can execute it transparently.
Using the minus symbol (-) before the command name as shown ( -LAYER) you can know input user date and control the command manually.
This can be very good when you start writing simple script routines.
Using the minus symbol allows you to use them with out turning of the following Filedia/Cmddia found within the (setvar) command structure.

the command line is moor faster

by using "ALIASEDIT" command u can make your own shortcuts.
it is very useful when we dont know the shortcut of a command or it is not familiar with us.