conceptually the same but totally different in execution, imo. difficult to explain, you'll just have to jump on it.
two main things for me were the weight(dirt bike...even a full size one is much lighter) and the tires/traction. balancing, apex entrance and exit are quite different.
love all things with a motor and wheels (be it 2, 3, 4 or impeller in case of a jet ski) and too many road rash to prove it.
love those mini's but unfortunately got too old (read too fat plus fear of injuries) to ride them. once you're older, you realized you're not as invincible as you once thought.