Why not both?
Repetetive side quests in a short game? I dunno, that doesn't sound so good...
OT: I feel like if quests are to improve your immersion, they have to be realistic. Being sent back to the exact same you just came from to get something isn't realistic, it's just stupid. That could've been a quest a bit later on in the game, and they could incorporate something else you might stumble over when going back to the Pumping Station to fetch that thing. That would be a lot more immersive than telling you to get back to the place you just frikking came for. It doesn't really answer the question, but it's kinda relevant.