"perhaps it might be of benefit to provide (possibly as one or more tutorials or meditations) a comparison of cpanminus to other common CPAN clients, "
I'm working on something as a background task, which has a hefty section on this very subject. I'll keep you posted.
"and thinking that if one were experimenting with different CPAN clients how much space could be "wasted" in the process."
cpanm has it's advantages, one being speed, it's simply a lot faster. It's also much lighter on resources, where cpan dies, e.g. installing things on an embedded, or otherwise resource limited system.