Hi Kim-
Bike shopping is exciting and a little bit nerve-wracking - spending money and being sure it's the right one. If the bikes are available in your size, have the shop do an approximate fit and take the bike out for a ride. Each bike will feel a little different to you, and choose the one that feels best. I just bought a new road bike and I found that the Trek, Specialized and Cannondale differed in the geometry slightly and in the way the bike handled. (They were carbon, not aluminum but generally they frames are similar within the brand.

For me, the Cannondale felt a bit more snappy in responding and the Specialized was more comfortable. Since I ride long distances but not fast, I preferred the Specialized

Good luck!