[dremd]

Warning : This post may not be 100% correct, but the principal is close.

Diesels benefit from injectors in 2 ways
1) better spray pattern
2) higher flow (more fuel injected near the optimal point for effectively increased timing)

Gasoline cars
1) Better spray pattern
2) SI (sequential injection) attempts to fire injectors only while air is flowing through intake manifold (mostly economy, no power because the pulses are far to long at WOT to restrict injection to the Intake cycle)
Check out the Megasquirt Site for great info on this.
3) (BIG MAYBE) smaller injectors on NON SI motor for better effective spray pattern.