It doesn't appear that there is an "update only" file.
 
I used to download the update-only files, but found that when there were problems with a new release (rare, but sometimes nasty when it happens) it was a real pain to find the older version of the file you wanted to replace. So I've been always downloading the full version for quite some time now. Of course, the fact that I can usually download a 40MB file in about a minute and a half may have some bearing on it....