He's a better presser (it's executed better)
He's more physical (very rarely gets knocked down, pushed off)
His anticipation is elite, he moves before the play, he gambles
Hold up play looks better
For Richi
Really good in the air, haven't seen that yet from Solanke (not saying he's brick, Richi's good)
Ability to play wide, he can cover Son, don't see that from Solanke
The other differences is really the space they play in, Richi is capable of playing in box, but is more wide, if in center, on the edge of box (again similarities to Son in the space occupied). Solanke is a box predator, he wants to be inside the 6 yard box
Both look like they will run themselves into the ground for the team.