FFXIV is set up with giant .dat files, and patches seem to redownload the whole file instead of trying to apply some binary delta. On the one hand, it's more download than needed (and unlimited broadband is not a global given); on the other, it's easier to verify that the files are what they're supposed to be. The PS3 patch is smaller btw - 2GB instead of 3GB.
It's certainly better than FF11 (where it downloaded 10000 small files slowly) for a patch.