New Vegas actually had issues with how many voiced lines there were cause they had to cut a companion who was taking too much space on the disk cause he had way too much dialogue because he was to be the singular companion who'd be sympathetic to the legion. And I( read that they actually had a limit on how much voiced dialogue they could have in the DLC so they had to plan it out and make the best of it, leading to tightly written DLCs (and them actually conserving lines enough to blow their load so to speak in old world blues with so much dialogue).
Though this is what I read and could be wrong. I do remember New Vegas having a lot of well written dialogue, especially in the DLC.