You can use the MultipleHostAccess property to filter local datastores out.
$cluster=Get-Cluster MyCluster
$dsNames=(Get-Datastore-RelatedObject $cluster|where{$_.ExtensionData.Summary.MultipleHostAccess}).Name
Get-VMHost-Location $cluster|where{$_.DatastoreIdList.Count-ne$dsNames.Count}|
Select Name,
@{N='Cluster DS Count';E={$dsNames.Count}},
@{N='ESXi DS Count';E={$_.DatastoreIdList.Count}},
@{N='Missing DS';E={
$script:dsEsx=(Get-View-Id $_.DatastoreIdList-Property Name).Name
($dsNames|where{$script:dsEsx-notcontains$_})-join'|'}}