I would never trade Lamine for Dembele, because the first is still 17yrs old and has a higher ceiling, and is a La Masia product.
Plus, aesthetically, as I explained above, Lamine is above all
That said, their effectiveness is pretty
measurable:
The last 2 seasons, Lamine has 0.58 non-pen goals and assists per 90 minutes, while Dembele has 0.75
Lamine has 0.58 non-p xG + xA per 90min, Dembele has 0.77
So Dembele is more effective for now, whether haters like it or not.
You can fantasize whatever you like about Dembele to channel your inner hate.
Truth is there though
Dembele stopped getting injured every other day with Koeman in charge, where the physical regime of the team changed. FACTOS
Pedri is not injured at all this season because he is doing special physical work at the gym
Players do not magically stop getting injured when older.
It happens by plan and training