I would not recomend the Bianchi Brava due to the Shimano Sora is not near as good as the Campy Mirage found on the Mercier. Plus unknown whether or not the Bianchi is double butted or not-the double butted 520 is a better design; and I also feel for your needs the steel frame is better. If you decide on one of the AL models however the Trek is using a mix of 105 and Tiagra whereas the Motobecane is all 105 and that stuff is far better than Tiagra (or Sora), and is about the same as the Campy Mirage; plus the Trek does not say if it's double butted AL or what type of AL.

You may want to check the frame warranty on each.

Anyway that's my spin on things.