Here is the link to the Trek site and the section where you can find the specifications on both the FX-series and Hybrid - 7000's series. One thing that stands out to me is the direction that the 'pendulum' swings on these 2 series. By 'pendulum' I mean as follows: Consider a Hybrid as a bike that is both like a mountain-bike and a road-bike. On some the pendulum swings more toward the road-bike - in terms of dimension, components, wheels. In the other direction it swings toward the mountain-bike.

Check out the Trek site and look at each the 7.3 and the 7300. Let us know what you think? Here:

http://www.trekbikes.com/us/en/bikes/bike_path/