Hey Roninpro!
Well cyclists on this Forum appear to be seriously divided on bicycle frame material types. I am on the steel side of things. I personally, feel as though steel will last for decades, if kept dry. It therefore, is more of an investment than just simply a purchase. There are many steel bicycle frames around today, in perfect working order, that have outlasted their original owners. Also with most bicycles, you can always upgrade the quality of components on a bicycle, as they wear out. In time, you can have a top class bicycle with the best components. It will look like a completely new bike, perform better than most, and its frame can be over twenty years old.
Aluminum has a shorter fatigue life than steel. Eventually, it will run its last cycle and the material will fail. Steel on the other hand, can operate on a daily basis and never reach any fatigue limit, because it has no such limit, that can be reached under normal working conditions. Steel is stronger and more durable than aluminum.
Steel has only one foe, and that's oxidation, or rust! If you keep it dry and protect it from the elements, you can pass your bicycle on to your grandkids.
Now, on behalf of aluminum. If you plan to race your bicycle, then either aluminum or carbon fiber would be best. However, in most situations, that's not the case, and steel wins by default!
Well, so much about frame material, let's move on to bike types....
Since you're mostly on paved roads, I think that some type of a road bike would be best suited to your needs. However, you might prefer a hybrid, since you've already mentioned the aluminum-framed Trek 7.1FX.
Road bikes have drop handlebars. Many hybrids look like road bikes, but they have flat handlebars. These are examples of the two different types:
Hybrid Bike
Road Bike
Which type would you prefer?....Drop or Flat Handlebars?...
(Click on the image to enlarge)
- Slim
PS.
Supportive Websites for Frame Materials:
www.brightspoke.com/c/understanding/bike-frame-materials.html
http://talu.com/materials.php
http://tetcycles.com/bikes/frame-materials/