No difference from the Final release version, to the one at windows update, just staggered the installation of SP2, this also offered the express install version (only installing those updates that you don't already have) about 66+ MB. This was supposed to help those on dial-up (me) and at 77MB no way will I be downloading that at 5KB per sec (on a good day).
The other option is the network install of SP2, about 277MB (contains all previous updates and new SP2 ones) available from windows download site.
This is only meant to be used for updating multiple machines, but no one is taking any notice of that. Having the full network install version means you have a copy of the full SP2.
This makes it easier if you ever have to reinstall XP from scratch (you won't have to download the patches again) and it is also possible to slipstream it and your original XP into one CD.