They've been learning spells. Kunon has been learning magic.
Yup. This right here is the biggest difference between them.
Tbf, in most manga/anime settings, you shoot fireball, and that's it. You're done. In some cases, you might add homing aspect to it, or multicasting to it, but fireball is still fireball. If Kunon were a fire mage, I bet he would be able to change its compression rate to make it smaller, thus faster and harder to be blocked, maybe it would have more mass so it could break thru some barriers, maybe it would split off into multiple fireballs on impact or on approach target, maybe changing the heat and make it super hot to be able to melt steel beams, or so hot it turns into Plasma Torpedo instead, or the power of the Sun, Nuclear, or Napalm.