What is MD?
A Markdown table is the one people actually write by hand: pipes between the cells, a row of dashes under the header. GitHub, docs sites and half the world's READMEs render them, and their one real subtlety is that a pipe inside a code span is text, not a column break.
What is JSON?
JSON is the shape data arrives in when it comes from an API. Tabular data usually lands as an array of objects, one per row, with the column names repeated as keys in every single one - verbose to read, but unambiguous.