MBTI is to Bill Gate's QDOS (Quick and Dirty Operating System that became MSDOS and the rest they say is history) as Socionics is to the niche world of MLM (Multi-Level Marketing).
How did i work that out?
Well, it's simple really, MBTI is more aimed at pigeonholing people unfairly by what they're are good for in terms of those Corporations. It nearly always focuses on what job you should be doing. This can be a source of much pleasure and pain.
On the other hand, Socionics from the good Russians (who got a man in space first i may add) have gone back to Jungian roots and done things better and more justly. There's little subjective suggestions of what is your best job as a certain type. Socionics is more of a neutral system that encourages your own self-evidence. In other words, it helps you to realise the obvious. The truth is not important; honesty is.