Koyasan and Kurashiki are completely different places.
Are you extremely interested in Buddhism & thinking about the life after this one? If so Koyasan may interest you. There are monks, vegetarian food and an extremely large cemetery.
Are you interests more secular? In what an old merchant town may have looked like in days gone by? Are you interested in art and food? Then Kurashiki is a pleasant and picturesque town with a very fine art gallery and some good restaurants.
The destinations are chalk and cheese.
Koyasan takes a little effort to reach and is on top if a mountain. Kurashiki is on the way to Hiroshima and easy to reach.
Edited: 29 May 2012, 14:38