Patching ESXi 5.x using esxcli: "instal" or "update"?

Hi community,

I'm just trying to apply the latest patch ESXi510-201303001.zip to my esxi host using command-line (no update-manager). I'm following guide from vmware knowledge base:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2008939

But I see there are two possible commands:

# esxcli software vib install -d "/vmfs/volumes/Datastore/DirectoryName/PatchName.zip"

or
# esxcli software vib update -d "/vmfs/volumes/Datastore/DirectoryName/PatchName.zip"

The only difference is "install" versus "update" and I did not find any explanation what the difference is. So which command should be used? Does it make any difference at all?