“[...] but why did you choose (Mandrake/Mandriva/)Mageia?”
Initially, because it was, IMHO, the best GNU distribution for beginners. I was no beginner, but I figured, I should know such a system well, if I was to recommend it and install it to other (newbie) people.
So I made it my main system, and over a decade has gone by =)
Nowadays, in its "Mageia incarnation", there's the added bonus of being a community-based distribution. Back in the day it was managed by a community-friendly company, but still a company.
Since, besides being newbie-friendly and community-based, it works really well, I've had zero reasons to change ;)