MBTI cannot be considered or treated as the same system as Socionics. If you have a type in MBTI, you cannot assume you will be the same or similar type in Socionics. Some very wrongly think you can treat Extroverted types as the same and just do a J/P Switch for Introverted types.
There are two reasons for why this is NOT the case.
1. The Four Dichotomies of MBTI mean something different in Socionics.
Extroversion/Introversion in MBTI has got a lot to do with how socially energised you are i.e. if you feel more energised around people or need time alone. In Socionics, this need for interaction with people specifically is more Ethics-related and indeed many Logical Extroverts in Socionics have little need for social interaction, their Extroversion being more about getting behind lots of projects rather than socialising. Similarly an Ethical Introvert in Socionics can be a very sociable person, requiring continuous interaction with those who they are close to. They just don't drive or energise the social scene like an Ethical Extrovert.
iNtuition/Sensation in MBTI is highly biased to the point where only iNtuitive people seem capable of free-thought and thinking outside the box. At the same time, the practical and daily competence of Sensory types is greatly diminished. In Socionics, Intuition and Sensation are far better balanced in their respective areas of capability.
Thinking/Feeling in MBTI has got a lot to do with being 'tough minded' or 'warm hearted'. While objective thinking is indeed connected to Socionics Logic, this is not necessarily going to make you more 'tough', 'competitive' or 'aggressive'. Instead, this is more related to Socionics Se, which means that many Se-types in Socionics become Thinkers in MBTI. At the same time, Ethics in Socionics has less to do with being a kind or generous person, but has more to do with your personal and interpersonal capabilities. Many more Se-valuing Ethical types may use their Ethics for social control and manipulation, rather than necessarily being nice and a 'bleeding-heart'.
Perceiving/Judging in MBTI seems almost entirely focused on organisation and planning. In Socionics, this is connected to Logic and not at all to Ethics. As a result, a lot of Ethics-leading types are going to be labelled Perceivers in MBTI. Instead, the Rational/Irrational dichotomy of Socionics focuses on whether you approach things in terms of how they should or ought to be, rather than how they how they are, which means that Ethical Rational types like EIE or EII can still be chaotic or disorganised, but have strong opinions on either what they feel is RIGHT or how people OUGHT to feel.
2. The Cognitive Functions of MBTI are different in their definitions to the IM Elements of Socionics. Parts of some are actually essential parts of others, leading to a mishmash or mix-up, rather than any clear correlation:
Parts of MBTI Se (living in the moment, pleasure-seeking, aesthetics) are covered by Socionics Si.
Parts of MBTI Si (memory, history, comparison, time-sense) are covered by Socionics Ni.
Parts of MBTI Si (rule-following) are covered by Socionics Ti.
Parts of MBTI Ti (e.g. figuring out how things work) are covered by Socionics Te.
Parts of MBTI Te (or just 'Jness') (power, command, hierarchy) are covered by Socionics Se.
Parts of MBTI Fi (e.g. emotional states) are covered by Socionics Fe.
Parts of MBTI Fe (e.g. relationality, social appropriateness) are covered by Socionics Fi.
3. MBTI primarily groups types by 'temperaments' based on pairs of dichotomies i.e. NTs being competent and clever, NFs being idealistic and warm hearted, SPs being free-spirited hedonists who like crafts and SJs being narrow-minded traditionalists without free thought. In Socionics the most important groups are Quadras based on valued Information Elements i.e. the fun-loving, analytical Alphas, the revolutionary, ideological Betas, the strategic, harsh-humoured Gammas and the peaceful, practical Deltas.