Rocket is the only truly criminal organisation of the lot, sure their activities are generally presented in a more child-friendly manner but it's evident they control a lot more things from the background than would seem apparent, and have no qualms about killing Pokemon and swindling their fellow men.
Another plus, although it might just be nostalgia's effects, is how uniforms look better — that pink/red R is unmissable yet somehow manages to befit them and not look silly.