Originally Posted by
GuitarBob
Given that I was pretty much stuck with an 11t cog, I went with 50/34 and bought both 11/25 and 11/28.
There's a 12-25 11 speed cassette in the 105 and Ultegra group. You could buy that and a 11-28 and make a 12-28 with less cash spent than a Dura-Ace cassette and also have a usable 11-25 cassette, too. You would need to decide which cassette gets the 16T cog and which gets the 18T.