Shouldn't there be a difference in first bounce because of balls size differences? I mean all balls will fall at same speed but basketball should bounce first because it's larger.
There is a difference in the first bounce as you can see in his demonstration. Unless you mean the first drop. In the real world heavier objects probably will drop slightly faster, especially if we compare balls like a beach ball and a bowling ball. While it is true that all object fall at the same rate in a vacuum, to make them believable you should animate them in a way that you would observe in real life.
I just want to admit that, although objects with different weights fall at the same time in a vacuum, however, in real conditions (with a presence of air) they fall with obvious different speeds because of air resistance.