Hello Brian, As you see Vista SP2 contains all the updates that were released since SP1, so by downloading via AU (Automatic Updates) you only get what you need, by downloading the full file you have everything plus you have it if you want it for later if you require it.

I forgot to mention that Vista SP2 contains all the updates that were released since SP1, so by downloading via AU (Automatic Updates) you only get what you need, by downloading the full file you have everything plus you have it if you want it for later if you require it. For Service Packs, download the full file and then install offline after