Derailleur gears require more maintenance, and are IMO not worth the effort for city cycling. Get a bike with a hub gear (Shimano Nexus 8, which is more efficient than Nexus 7 or 3). If the terrain is flat enough, you could even opt for single gear. If you get a belt drive (instead of a chain), practically the only remaining maintenance are tires and brake pads.
+1 for hub gears - you just have to unlearn the habit of shifting gears while pedaling, because that can destroy your hub gear. And not lend your bike to anyone who might accidentally do that. Funnily enough, most bike sharing bicycles where I live have hub gears anyway, and many are in a pretty bad condition, I assume because they were used by people unaccustomed to hub gears...
Hub gears are simply amazing. Combined with a belt drive, they require almost no maintenance and they are completely silent. The best part is shifting gears while stopped. It's really useful in the city.
I'm building a gravel bike with drop bars, disc brakes, a steel frame and an Alfine 11 hub gear and a belt drive. I can't wait to ride it.
