It seems to me that he lacks the flashiness of Pogba - of course, you can alternatively phrase it as 'consumate artistry' or something similar. Pogba hit real dazzling heights. But he only hit them occasionally, and had a sort of childish quality to his attitude a lot of the time.
Mainoo also has a very high ceiling, but probably not quite as high. On the other hand, he's consistent, calm, remarkably mature for his age, and blessed with football intellience. I for one am more than happy to take that small drop in artistry to have consistently very good player with an excellent interperosnal style about him. Out of those two, give me Kobbie any day.