Similar question was answered here:
The difference is known by answering the question "Is VSE already installed, or not?" as that tells you which package you need.
The mentioned thread goes into further related topics too which might be of interest to you.
The link in that answer to another thread is not there anymore.
So In plain English:
I have another version of the Agent installed I use the Update install
If I have no Agent Install I will use the Repost.