Without getting into the world famous steel vs aluminum flame war here are some web sites for your to study, then make up your own mind.

For a scientific non-bias view: http://www.exploratorium.edu/cycling/frames1.html Click on the bottom right on the small white arrow to read more pages (4 total).

For a scientific bias view: http://www.anvilbikes.com/story.php?news_ID=11&catID=3 Read the related items as well because there's some excellent info hiding in there.

For bias view: http://www.henryjames.com/faq.html
http://www.kirkframeworks.com/Philosophy.htm
http://rivendellbicycles.com/html/101_pureopinions.html
http://rivendellbicycles.com/html/1...ematerials.html Also read Rivendells other subjects of interest.