Originally Posted by
seypat
So, pick your drivetrain. A double in front and whatever you want in back. You are hammering down a hill on your big/small combo. At the bottom you come to an up that sends you to your small/big combo, or close to it. You top that hill and back to your big/small combo. Each time you are hitting those STIs to move that drivetrain however many cogs it takes. All of those other 2-3 cog shifts as well.
I have never desired to go from big/small to small/big as one change, and I ride some pretty hilly terrain. If I ever even need to downshift the front without going up a few cogs in the rear I'd guess that I was totally sleeping/ignoring the signs that I should have been shifting long ago.
That said, with Campy Chorus it would take one push on the left shifter and and three on the right to go big/small to small/big using an 11 speed cassette. Going small/big to big/small would be one of the left and two on the right.