Trisomy 21 occurs via Nondisjunction in which stage?

Hey guys,

I drew out the nondisjunction in both meiotic stages and it seems like nondisjunction in either of the meiotic stages (MI and MII) can yield a zygote with trisomy 21. Same for Klinefelter's syndrome.
Is one meiotic nondisjunction favored over the other for particular aneuploidies or can these genetic defects result from either nondisjunctions?

Thanks!