One's in the past tense and one in the present, but we do use both to refer to a situation that happened in the past (the breaking of the vase!) I'm sure there's some subtle difference, but I would always use "the object is broken" if I am observing that an object is damaged, but if I am referring to the process of it breaking (having just happened) I would say "the object has broken!" I hope that makes sense and other anglos would agree...