High Grade kits are 1/144 scale, run roughly 100–300 parts, and build in a weekend; Master Grade kits are 1/100 scale, often 400+ parts, and add a full articulated inner frame under the armor. HG is the hobby’s mainstream — huge selection, low price, fast wins. MG is the enthusiast tier — bigger, heavier, more engineering, more hours.
Our standing advice: build at least one HG before your first MG. The skills are identical; the MG just asks for more of them, and finishing a kit teaches more than stalling halfway through an ambitious one.
Go deeper in our kits & grades guides.