Seat post for carbon framed bike

I am thinking of buying a Cube Agree GTC Pro, and it will come with a 31.6mm dia seat post. I see that Cannondale Synapses come with a 27.2mm dia post apparently for extra cushioning. Anybody got knowledge of if the smaller dia post is noticably better? Can you buy a sleeve that will allow fitment of a 27.2 post to the cube?
0
Posts
27.2mm post are lighter and less stiff which is the point. 31.6mm posts are used on large diameter seat tubes which are used to increase frame stiffness. You could just fit wider tyres or drop tyre pressue though for bigger change.
Also worth considering is a Syntace P6 carbon post - these are available in a 31.6, and are designed for some flex etc.
Reviewed on this site here:
http://www.bikeradar.com/au/gear/category/components/seat-post-seat-pin/product/review-syntace-p6-hiflex-seatpost-12-46314
Shims are available but it will look like a dogs dinner with the thin post eminating from a thick tube.