It to do with mapping, better(top end) power with the injectors pointing straight down the throat, where the extra ones are.
Software has got a lot better as more tuners do more experiments as well.
Two smaller injectors will ALWAYS produce better results than 1 large one.
Some run smaller ones lower down then onto larger or mix of both higher up.
In an ideal world they need to be as close to tyhe valve low down as possible but further away possible higher up so it is a compromise on most 4 injector cars.
tabetha