the weight of that alloy one looks iffy ..6.95kg!!? My Canyon CF has a claimed (and actual weight) of exactly that
It has exactly the same wheels, groupo etc , but mine has a frame weighing 950g. I'm dubious as to whether an alloy frame can be anywhere near that weight, especially not at that price.
6.95kg is for a 53cm frame. The 56cm frame itself is 1,170 grams
Review suggests the 58cm Carbon is 7.4kg
What do you a want from your new bike that your alloy Defy does not offer? Weight? (not so hard to achieve) Stiffness (will depend on the tube diameters and carbon layup)? Better components? (Easy upgrade). Exclusivity (Need lots of cash!)
Whilst the Defy has "sportive" geometry, it's a very nice blend of race, endurance and comfort. Of course the headtube is a little longer than a classic race bike - but only about a cm. The steering is half a degree slacker than a TCR, but you will not notice. The bike is much less of a sportive compromise than equivalent offerings from Specialized and Cannondale which have very long headtubes. Ask Mr Degenkolb what he thinks of his Defy#.
I'd personally recommend the Carbon Defy Advanced with 105 and save for some shiny lighter bits. That frame was £1500 and Bike of the Year in 2013. Great bikes do not stop being great just because they are running 105 - read Ultegra 6700 with better shifting.
#Or me, we have an alloy Defy and a carbon Advanced SL. They are both great. Also have other alloy and carbon race bikes to compare.
TiRed, not quite sure what point you were trying to make. Why would I buy a more expensive, lower spec'd and heavier bike (Defy Advanced) than the ones I identified in my OP. I have already reviewed the potential alternatives and decided on the Radon(s). I already have a defy so am aware of their virtues.
My point was the first "What do you want from your new bike that your alloy Defy does not offer?".
And will frame material deliver that? (maybe, maybe not). But there are many other factors to consider. And if you are pleased with the virtues of one bike (geometry for example), then you will always compared your next to it. And you want it to compare favourably 😉
And based on the geometry of your two choices, Alloy. The carbon is either too slack or too steep depending on size.