If you can afford the extra go for the Cf. Nothing wrong with the alloy Canyon but the Cf will give you a subtlety nicer ride. I’ve ridden alloy and Cf Canyons and there is a difference, don’t believe people on here who say there isn’t . £400 better that’s for you to decide. Personally I always get the best bike I can afford, for me it adds to my enjoyment of cycling. For others just riding is important, they care little for what they ride. That’s great but some have a tendency to sneer a bit at others who like nice bikes and kit.