Shimano Cassette 10 Speed Teeth Selection I am planning to upgrade my drivetrain and I'm in the process of selecting the various components. My bike currently has a Shimano Tiagra CS-4600 10 Speed Cassette 12-28t.  I am looking to upgrade to a Shimano 105 5700 10 Speed Road Cassette. The 105 doesn't have a 12-28t so I was wondering based on the following options (below) what would be the closest to what I am riding now?


11-25t  
11-28t
12-25t  
12-27t


I am guessing the two in bold would be the closest options. Here's some additional info if it helps:


I currently have a compact 50/34t 110mm crank. Plan to upgrade from FSA to Shimano 105 5750 Compact 10sp Chainset (same ratios).
I live in a fairly hilly city (Seattle, WA) and ride mixed terrain hills, flats, gravel (short and long rides). Basically everything but steep mountain passes.
The existing 12/28t seems to suit me fine.
The problem is the Tiagra 12-28 is kind of special as it has a more gradual transition between ratios and less aggressive gearing all the way to the middle of the cassette, where the 105 and Ultegra cassettes with a similar total range have a less gradual change and drop much more quickly into more aggressive ratios.

We can compare the tooth counts to see this:

                 1   2   3   4   5   6   7   8   9  10
-------------------------------------------------------
Tiagra  12-28:  28  25  23  21  19  17  15  14  13  12  
   105  11-28:  28  24  21  19  17  15  14  13  12  11
   105  12-27:  27  24  21  19  17  16  15  14  13  12


I personally found that 2 tooth difference in gears 3/4/5 to be highly noticeable for casual riding, especially gear 3, as I personally use that with the big ring up false flats.  

This seems to be true of all of Shimano's higher end road cassettes.  I would hazard a guess that these are viewed as being more "race" oriented, where you need to tackle a couple steep sections then you would drop back quickly back into the standard race gearing on the flats.

The closest match to your current 12-28 is a  12-30:

                 1   2   3   4   5   6   7   8   9  10
-------------------------------------------------------
Tiagra   12-28:  28  25  23  21  19  17  15  14  13  12  
Ultegra  12-30:  30  27  24  21  19  17  15  14  13  12


However I am not clear on the max sprocket of the 5700 derailleur.  I have seen it listed as 28T in some documentation, more in other.  Perhaps this could be separate SE question.