I am looking at getting back into bike riding after wanting to for the past few years. I am looking at two bikes mainly (trek 7100 or trek 7200). I am having a hard time figuring out what is different. I can look at the spec sheets and see they use various different components but other then that it means nothing to me. I would also be willing to step up to a 7300 if it offered any significant advantages. Could anyone shed a little light on this subject for me? BTW this bike will be used mostly on city streets/sidewalks, slightly hilly. And an occasional finely ground dirt track.