Mandarin would be more useful since it's spoken by more people, but I prefer Cantonese because of its preservation of final consonants. Mandarin has a much narrower phonotaxis.
This post was edited by Benedict Arnold at January 11, 2018 6:04 AM MST
I once bought a course to learn Chinese. The first 13 lessons were on how to draw the characters.
A few years later I signed up for an online thingy and worked on it for a couple of months. I learned something like 200 words. No clue about sentence structure, verbs or nuthin. Just words. (Did you know 'explode' is a valid Chinese cooking term?)