$0.02 - I'd roll with the road bike. The easiest way to determine the gearing is ride around without shifting for a week. Pick the biggest gear you can ride up the biggest hill without having your kneecaps pop off your legs. Also, are you a seated or standing climber? If you sit, go with an easier gear. Actually, that's not a bad idea overall. A bigger gear will mean more speed on the flats, but slowing down without using a brake will give your legs a major workout at first. I'd ease into it. You can always switch to a 53x11 down the road...