Why do some dancers get sore feet whereas others get sore legs?

Different foot types: Keep in mind there are different foot types. Some people have high arches, others have average and some have flatfeet. So the biomechanics of the different feet will function differently.

Dancing: It is related to the particular dancer's bone structure and mechanincs of gait and dance. How the foot, ankle and leg muscles, joints and bones interact and react to the pressures and forces placed on them in dance, especially en pointe, will vary widely between one dancer and another.