Scripting Automatic Updates to get the Recommended updates, not Important or Optional

Question

Where I work the policy is to download Recommended updates, and I'm getting very tangled up working out how to select them with a script. Can anyone help me please?
If my query includes AutoSelectOnWebSites=1 then I get the Important updates. Without that I get the Optional ones. I'm getting the impression that the Recommended ones are chosen by the Windows o/s, not by the web site, but I'm not sure and can't find
the algorithm.
Here's the relevant part of the code I've got so far.
 If ($UpdatesRequired = $True) {
#  $SearchQuery = "IsInstalled=0 and Type='Software' and IsHidden=0"
  $SearchQuery = "IsInstalled=0 and Type='Software' and IsHidden=0 and AutoSelectOnWebSites=1"
#  $SearchQuery = "IsInstalled=0 and IsHidden=0"
#  $SearchQuery = "AutoSelectOnWebSites=1"
        try {
            $SearchResult = $UpdateSearcher.Search($SearchQuery)
        } catch {
   $SearchError = $error[0]
   $OutputString = $OutputString + "ERROR: searching for Windows updates failed, the error message was $($SearchError.Exception)."
   Write-AppEventLog -EventType Error -MessageText $OutputString
   Return
  if ($SearchResult.Updates.Count -eq 0) {
   $OutputString = $OutputString + "No new updates were found."
   Write-AppEventLog -EventType Information -MessageText $OutputString
  else {
$i = 1
   $OutputString = $OutputString + "$($SearchResult.Updates.Count) new updates were found, checking which to select...`r`n`r`n"
   # most of the next code is copied from
http://sushihangover.blogspot.co.uk/2013/01/installing-windows-updates-via.html#!/2013/01/powershell-optimize-volume-vs-process.html   
   $UpdatesToDownload = New-Object -ComObject 'Microsoft.Update.UpdateColl'
   ForEach ($Update in $SearchResult.Updates) {
    $addThisUpdate = $false
    if ($Update.InstallationBehavior.CanRequestUserInput) {
     $OutputString = $OutputString + "Skipping: $($Update.Title) because it requires user input.`r`n"
    elseif ($Update.Categories -contains "68C5B0A3-D1A6-4553-AE49-01D3A7827828") { 
     $OutputString = $OutputString + "Skipping: $($Update.Title) because it is a service pack.`r`n"
    else {
     if ($Update.EulaAccepted -eq $false) {$Update.AcceptEula()}
     $addThisUpdate = $true
    if ($addThisUpdate) {
     $UpdatesToDownload.Add($Update) | Out-Null
     $OutputString = $OutputString + "Adding: $($Update.Title).`r`n"
write-host "$i patches selected for download"
$i++

Answer 1

Thanks for this jrv and I do like your signature by the way. I've had a long look at the most popular script in the gallery for Windows Update, this one:
http://gallery.technet.microsoft.com/2d191bcd-3308-4edd-9de2-88dff796b0bc. Also loads of others on the internet.
Some download everything, and the ones which don't select updates using a criteria with the search as per
http://msdn.microsoft.com/en-us/library/windows/desktop/aa386526(v=vs.85).aspx, and/or filter the search results using the IUpdate properties
http://msdn.microsoft.com/en-us/library/windows/desktop/aa386907(v=vs.85).aspx.
I don't think there's an IUpdate property or search criteria which correstponds to Recommended updates, I can't see one anyway and I've spent ages looking. I'm wondering if Windows chooses, not the web site, based on its knowledge of what's installed.
The AutoSelectOnWebSites property isn't what I need. It selects updates which the Windows Update gui calls Important when "Give me recommended updates the same way I receive Important updates" is
unticked. The requirement where I work is to install the Recommended updates. I've tested it several times and I've confirmed that on plenty of the Recommended updates
AutoSelectOnWebSites is set to false (on all of the updates in the example below)
Here's an example:
With "Give me recommended updates..." unticked I get:
With "Give me recommended updates..." ticked I get:
I think I need to know how Recommended updates are selected, and I can't think of any more digging I can do. Jrv, if you or anyone else knows I would be grateful!