Well, I have a background in both.
Before getting my first UNIX contact, via Xenix in 1994, I was already fully comfortable with the GUI world of Amiga and later on PCs. Including GUI alternative environments like Smalltalk and Oberon.
So, although I do master the CLI, I rather spend my time in the cosy GUI world.
I don't think this is something that follows age lines. Whether or not somebody primarily has a background in the FOSS world or in the Windows universe is probably a much stronger indication of what sort of tools they use.