One thing is that I think a neuro would be more able to rule out other disorders that can mimic autism (e.g. Landau Kleffner, other seizure disorders). Whereas a dev. ped might be coming from a more pragmatic standpoint of "Does this child have the same characteristics as a child with ASD and would they benefit from the same support".
I have a good friend with a child who has an "official diagnosis" of Childhood Disintegrative Disorder from his neuro. However, at this point he function exactly like a child with HFA. His parents use the HFA label when they're trying to put together interventions for him etc . . . but from a medical perspective there are certain differences in onset and perhaps etiology between the two.