Use what you want. Use what makes sense for what you are doing now.

While I'm mostly a command line guy (I use the GUI only to get a graphical representation of reversion graph), I've trouble to understand why you think using the command line gives you a better understanding of what happens behind the hood (well excepted for GIT :)), usually there is a clear mapping between the two even if CL may give you access to some little used features.

Now in my opinion, automating what can be automated in the process is part of the job and for that, CL is mandatory.

Use what you want. Use what makes sense for what you are doing now.

While I'm mostly a command line guy (I use the GUI only to get a graphical representation of revision graph), I've trouble to understand why you think using the command line gives you a better understanding of what happens behind the hood (well excepted for GIT :)), usually there is a clear mapping between the two even if CL may give you access to some little used features.

Now in my opinion, automating what can be automated in the process is part of the job and for that, CL is mandatory.