Beginning in PowerShell 4, you can use the Where() and Foreach() methods in place of Where-Object and ForEach-Object whenever you do not want to use the streaming mechanism of the pipeline.
So if you already loaded all data into a variable, the non-streaming mechanism can be faster:
$Services = Get-Service # streaming $Services | Where-Object { $_.Status -eq 'Running' } # non-streaming $Services.Where{ $_.Status -eq 'Running' }
To save resources, the most efficient way remains the streaming pipeline mode, and not using variables:
Get-Service | Where-Object { $_.Status -eq 'Running' }
Note that Where-Object and .Where() use different array types, so their output is technically speaking not identical:
PS C:\> (1..19 | Where-Object { $_ -gt 10 }).GetType().FullName System.Object[] PS C:\> ((1..19).Where{ $_ -gt 10 }).GetType().FullName System.Collections.ObjectModel.Collection`1[[System.Management.Automation.PSObject, System.Management.Automation, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]
