Hi and welcome to the Chiari forum.
Yes, it is possible to get different opinions from the same set of films....the issue is not if Chiari is there, but if the Drs reviewing them believe Chiari is something that needs to be addressed.
Chiari for the most part is new to many Drs and their radars as MRI's were not always around to detect them, and once found, what did it mean? To many not much as they feel the tonsils herniating is normal due to gravity....and others only use the length of the herniation to classify it as Chiari, when Chiari is the malformation of the skull which results in the herniation....so very frustrating for those of us dealing with the symptoms which again, many Drs refuse to Believe occur.
Get and keep copies of ALL testing reports , MRI's on disk....make copies and get as many opinions u can get, but research the Drs first to locate true Chiari specialists...(they research Chiari and know the cutting edge treatments).....we do have a list of Drs for u to use in researching Drs, the list is compiled by the members here of Drs they have been to, treated by and liked....the list is NOT a referral nor an endorsement for those listed on it....
http://www.medhelp.org/health_pages/list?cid=186
If u have ne questions feel free to ask, we will do our best to help guide u thru this...know u r not alone <3