AFAIK Aricept is only licensed for use with Alzheimer's Disease. It is therefore not prescribed to people who have other dementias, such as Vascular, although it can be used if there is mixed dementia with an Alzheimer's component.
I believe that Aricept is the drug of first choice within it's class, in that they (Aricept, Exelon and Reminyl) have the same basic way of operating, but Aricept is the one that is least likely to cause side-effects.
My dad began on Aricept, and responded well to it, but was switched to Exelon, because it is considered to be more helpful with people who have psychotic symptoms associated with their dementia.
We were warned at the time, that Exelon has a far bigger "reputation" for more commonly causing the side-effects associated with these drugs, and that if side-effects occur they are likely to be more severe as well.
Certainly, dad's Exelon was titrated far more cautiously than the Aricept was.
Of course, much depends on the experiences and opinion of the prescriber, but it is my understanding that Aricept is normally the first to be tried, the others are more for a "fall back on" treatment.