Actually its been tested many times (check the wow forums); Duel wield is round 20-24% miss rate and normal miss rate is 8-16% so there is a major difference, however, at the same time, you will be missing more but you will be swinging much more. Ultimately damage really depends on equipment, if you got 2 amazing 1h weapons you will tear stuff up just as well as if you had an amazing 2h weapon. Once again go to worldofwarcraft.com forums, lots of parsing data there to mow through.
To keep going, if you want to duel wield you basically HAVE to go fury, which include an extra rage per hit talent so rage actually generates MUCH faster with duel wield, and that translates into damage, so in the end it bout equals out with 1h+shield and 2h. However, the key to being a good warrior is to know how and when to switch your config multiple times in order to make best use of your talents (all the flat +dmg talents are best with 2hs) pick up your shield when you are getting the sh*t beat outta him, and than take out the duel wield when you want to go pure offense and tear into things in turn.
Edited, Tue Dec 21 14:20:30 2004 by Trixierix
Edited, Tue Dec 21 17:19:19 2004 by Trixierix