When you absolutely, positively need the big guns for a big, fast ride…
Or for fun, when you just feel like cruising (though more than worthy in the event a real ride breaks out):
I’ll be writing more about the differences betwixt the two bikes above, but for today suffice it to say the Venge, watt for watt, is worth 1 to 1-1/2 mph over the Trek. It’d be closer to 1-mph if I put the 38s that currently sit on the Trek on the Venge – both bikes have 10-sp drivetrains so this would be easy as swapping wheels.
The Trek has a lot of pull, though, because that bike, my bike, was handmade in the USA. Everyone has their frames made in Taiwan nowadays.
Anyway, everyone should be lucky enough to have to make the hard choice of which one to ride.
Today is one of those, “when you absolutely, positively, have to get there fast” days. The Venge is all dolled up, ready to go.
Fit Recovery 
If I run the same 60mm wheels on my Trek 5200 and Canyon Aeroad there’s only like half a mph difference in overall speed. Where I tend to notice the most difference is punching over short/sharp climbs, sprinting out of corners, etc. The newer bike does everything just that bit better. As you say, it’s great to have the privilege of choice!
Yeah, I think the aero properties have a little to do with it but the big deal is the layup of the carbon, size of the bottom bracket shell, and how the newer bikes jump when you push on the pedals.
They certainly do! 😁