The Fresians I have seen around here I would put around 16 hands.  Fresians as a breed seemed to be pretty tightly clustered in their genectics in that there does not appear to be much diversity in the breed.  Somebody who breeds Fresians I am sure is going to be able to provide a more detailed answer on the genetic diversity within the breed but within a standard size breed of horse I don't know if I would consider a variation between 15 and 16.2 extreme.  I would say if you have a choice between these two I would go for the 16.2 but that is my personal preferrence.