Originally Posted by
Gege-Bubu
The course I am training for is pretty flat. But I ran it last year and found that 28 will make it easier. But I would like to know, if training harder on 12-25 will give me any advantages if i run my race on 12-28
I don't think so. the two cassettes just offer slightly different gear combinations and the only ones that matter are at the top end of the cluster for when you are struggling up a steep section.
What kind of race is it? A road race? A time trial?