Giant Defy 2.5 a worthwhile upgrade

baileyjb

I am currently riding a Cannondale CAADX 105 cyclocross bike with upgraded chain rings making is a compact and also running road tyres as I am using really for road use. I am happy with the bike and my next upgrade was going to be to full carbon. Over the weekend I have been offered a Giant Defy 2.5 for £250. I I know the group set is not as good as the Cannondale but was wondering is its worth getting for the frame. Then swapping my Cannondale 105 groupset to it. Do you think I will see any difference (on longer 60 mile plus road runs) or should I keep the money and keep saving?