If we're back talking about groupsets, I'll add my tuppence worth. In terms of performance the top end sets (Dura Ace and Record etc) really do take the biscuit and they're lighter. However, the lower top end stuff, if you know what I mean, is probably better value. ie: Campag Centaur is essentially 3 year old Record for a much more affordable price.
Top Velo noted about Shimano's groupsets that 105 is great with Dura Ace being obviously better but for signiicantly more cash. They also pointed out that for the difference between 105, Ultegra and Dura Ace in terms of price and weight (and kudos) there is really no sensible reason to buy Ultegra - spend mor on DA if you can, if not save yourself a few quid and get 105.