don't know much about how MA's are educated and so I cannot at all speak to differenced between LPN & MA ed (and I am an RN).
Most nursing programs
are structured around a foundation of knowing anatomy and something about the sciences (often including chemistry and microbiology and more, taught at the college level). Nurses then learn general care procedures of hospitalized patients and then learn about normal and acute and chronic care in the domains of medical surgical, ob-gyn, psych and pediatric nursing. Rather than learning skills per se, they are learned in the context of caring for a person experiencing a bio-psycho-social problem or alteration in health. Nurses create and implement a plan of care for individuals based on a framework of assess, plan, intervene and evaluate.
My perception, and I would certainly invite you to broaden my knowledge base, is that MA's learn about certain care procedures and may have a limited and not usually college based knowledge base in anatomy, physiology, pathophys, micro, psychology, sociology, nutrition.
The procedure of isolating a superficial vein, cleaning an arm and inserting a needle is relatively easy. The understanding of rationales for when and why you do and do not perform certain procedures or inject certain substances is not so easily taught. In a case management job I performed, we taught parents to care for their vent dependent children and they did it expertly, but their knowledge was not highly generalizeable and they were not qualified to care for all children on ventilators (as professional peds nurses are).
Mobility is very individual based on the state board of nursing that licenses LPN's in your state and, alas, it would not surprise me if their is easy upward mobility between the LPN and the MA. I will keep my thoughts on that to myself; they have nothing to do with you as an individual since I don't really know you at all.
Again, your own state board of nursing can address the mobility between MA and LPN and you can link to your state board of nursing from this web site's home page.
Good luck in your future.