pay attention that while both painters are naive
Modigliani paintigs feel like Renaissance, with round
women , soft unbroken figures.
picasso is many times a cubist , he is wilder and
strogner in angles.
Modigliani's life were much poorer that picasso's
and as such his paintings are less agressive , gentle
and modest.

those are few differences in very general.

answer was written by ohad stern