Thanks for all the feedback. I do all my own bike maintenance as well so not too worried about keeping it functioning correctly.
The big advantage like Berettafan says is the buttons, and in more than one spot. Right now shifting the tri bike is a pain if you are not in aero, especially when climbing. The slice is set up for Di2 with the seat tube battery mount already there etc. But I think the Etap is a bit lighter without the battery needed in the Di2...
old times, I remember racing as a teenager with a 16-20 rear and 48/52 front. Almost like having a single speed...
Bill, the gearing is the same on both bike 11/28 and 36/52 but the Supersix has 172.5 cranks and the Slice has 165mm cranks. I am contemplating going 11/25 on both bikes.