I'm a new rider, and my bike is a 7.5 fx wsd. At a hair under 5'5", I went with the 19" and have been very, very comfortable, but I have along torso and I like to go fast. I looked at some of the more cruiser/commuter geometries, and briefly had a 2nd hand 14.5" 7100 wsd, and this was a better fit for me.

NB, the 19" wsd and the 17.5" men's frames for the 7.5 have very, very similar measurements. I rode both and it was a close decision. The geometry charts are available on Trek's site or at your LBS.

Also, the other bike I really liked was a 1.5 wsd - a road bike. If you prefer a hybrid with more mountain or cruiser geometry, the 7.5 might not be the right bike.

I went with the 7.5 instead of the 7.3 on the hypothesis that it will take me longer to developmentally "outgrow" the 7.5. No idea how accurate that is, but it's what I tell myself. I did/do prefer the 7.5's carbon fork (vs the 7.3) on bumpy roads.

Oh - and the satin carmine is much less pink-toned in person. I was relieved.