Yes instruments is one thing, at least for orchestral you need 3rd party libraries to really be able to do professional sounding tracks. But effects, wow I am so impressed with the ones you get with Logic, great range of effects, amazing quality. And I have been using a LOT of effects over the years in many different DAWs. Logic truly delivers on this aspect.
Granted there are some effects lacking, but they might add more in future upgrades. Also they have some unique ones that I love. Like phat fx and step fx, particularly step fx is utterly amazing!