For city road rides up to 30mi or so, I prefer my hardtail MTB with 60+psi slick tires to my "road bike". I ride a narrow flat bar with bar ends, a flat stem, and high seat so my riding position is sort of similar to a road bike. I keep my suspension fork screwed down tight with little sag when roading. Sure I'm not quite as fast as on my road bike, but so what? With this set up I can ride many miles with acceptable pedaling efficiency and still stay nimble in a potentially hostile enviroment (e.g. keep my ability to jump a curb & go off road if some misguided SUV tries to make me into a hood ornament. It's happened to me more than once!). FWIW- I regularly ride my 30# FS bike 4-5mi each way to a local MTB trail. The roadies give me dirty looks for riding FS on asphalt, and the "hard core" MTBer's frown at me for not transporting my MTB to the trail by car. Who cares! The road ride serves as a nice warm-up/cool-down for my trail rides.
Bottom line: Cycling is about enjoyment and exercise. Pick a good biking group & ride what you like!!!!!!