CD <- Coefficient of Drag is the name of the game on the flat. The lower the better. If a salesman says to me that bike A is faster than bike B then I would ask him/her "show me the independent wind tunnel test that determined the CD for bike+rider for each model"
When you get into the hills then it's strength/weight ration, and IMO if you can't climb on a sub 25lb bike then the limiting factor is not the bike.
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"Surely one can love his own country without becoming hopelessly lost in an all-consuming flame of narrow-minded nationalism" - Fred Birchmore