You probably have to change the collision hull of the entities. You can do this by calling 'c_setminxmax(entity_name)' after you've created the entities...
Code:
ent1=ent_create("mig.mdl", vector(100, 300, -70), cub1);
c_setminmax(ent1);
set(ent1,POLYGON);


ent2=ent_create("mig2.mdl", vector(-240, 200, -70), cub2);
c_setminmax(ent2);
set(ent2,POLYGON);


Also 'POLYGON' should only be used on 1 of the colliding entities. It's not really meant for moving entities either.