Originally Posted by
banerjek
Get a 12-27.
The spacing is exactly the same as a 12-25 except the last two cogs so there's literally no difference for the gears you use the most. In practice, whenever you need the 25, you need the 27.
There is some truth to that. I never had a cog larger than 23 until about 4 years ago. I got a 25 and all of a sudden I need that gear. More seriously, it was nice having that bailout gear even though I hardly ever used it. Now I use it more frequently. I don't know what if anything that implies about my cycling. Maybe I should try a 27 just for grins and see if it becomes necessary.