The difference is if a getter/setter method is called by the ORM implementation or not. If your Annotation is on the getter, then the getter/setters will be called when the ORM sets and gets the data, if the Annotatation is on the field, then the getters and setters are not called.
So the question is do you need to add special code in your getters and setters that you also want the ORM implementation have to call or not. If not stick with field.
The getter/setter option seem very tempting because you have the chance to manipulate the values of memebers before you return them. However, If you have validation codein the setter methods, you may encounter a situation during the development, in which you read several records from the database , one record does not match the setter validation rules, the set method fails (hibernate use it to populate the object with data from a db record) and the whole read query fails.
This may also happen if you have a bug and the data in the database is corrupted (does not match the validation rules), you usually wouldn't want to fail the whole 'get many records' action because of one corrupted record.
Anyways, you candecide otherwise but this is the trade-off.