The roles vary widely in what you do, how much patient contact you have.
Interview people who do these jobs if possible. LPN's have decent job mobility and their job usually brings them into direct care roles where they administer medicines (alot of responsibility), give direct care (change bed linens, clean up people, assess, evaluate out of limits vitals, report and act on abnormals). They have a better background knowledge to do patient education. LPN's have good job mobility and _may_ work in hospitals, care homes, doctor's offices, schools
, home health agencies, industrial settings to name but a few. they have good mobility to the RN role with 1 + 1 ed programs.
Medical Assistants work within doctor's offices and I imagine that a skilled and intelligent MA can find themselves in a number of settings, too, but their credential and preparation isn't as uniform and known as the LPN. The emphasis is on doing a technical task and their is less emphasis on interpeting and acting on (beyond reporting) abnormals.
Neither role is inherently better, it is simply a matter of what you prefer to do.