I
think it depends on what breed the dog is. For example it might be more
informative to list a large teacup Chihuahuas weight in grams. That
would tell you the large Chihuahuas weight relative to other large
Chihuahuas. On the other hand a large Old English Mastiffs weight given
to the closest kilogram would tell you plenty about the dogs size
compared to other large dogs of that same breed.
However I think the correct answer is kilograms.