I use the command line all day every day. I also use SourceTree, however, maybe 3-4 times a day to see something visually (to commit a hunk, to quickly add individual files to a commit, etc).

I'm intermediate with git at best. I don't do anything fancy. I pull, branch, merge, push, and that's basically it. All day. I've used bisect precisely once about a year ago, I still don't know what rebase does... But I'm rock solid on the stuff I do know.

Given that I do things like:

git co -b feature/new-menu

git pull

git merge staging

git push

git co staging

git pull staging

git merge feature/new-menu

git push staging

Hundreds of times a day, there's simply no way it's faster to do it in a gui. I can type git co staging, git pull, git merge feature/whatever, :wq ( to close vim ), git push in probably 4-5 seconds now. I don't even think about it when I type it I've done it so often.

Get that fast at it and then invite your boss to watch. There's no way anyone could be convinced that a gui would be faster for me if they watched me pushing/pulling/creating/merging branches. They wouldn't be able to keep up.

(not a brag at all btw. These are simple tasks done hundreds of times every single day. You get really, really fast with that!)

good luck!