Compare-Size.ps1

Param(
    [Parameter(Mandatory=$True)]
    [string]$Original,
    [Parameter(Mandatory=$True)]
    [string]$Compare
)

$OriginalSize = (Get-ChildItem $Original | Measure-Object Length -Sum).sum / 1Gb
$CompareSize = (Get-ChildItem $Compare | Measure-Object Length -Sum).sum / 1Gb
[string]$Difference

if ($OriginalSize -lt $CompareSize) {
    $Percent = [math]::Round(((($OriginalSize / $CompareSize)-1)*-100),2)
    $Difference =  "$Percent% Larger"
} else {
    $Percent = [math]::Round(((($CompareSize / $OriginalSize)-1)*-100),2)
    $Difference = "$Percent% Smaller"
}

Write-Host "Before:"("{0:N2} GB" -f ($OriginalSize))
Write-Host "After:"("{0:N2} GB ($Difference)" -f ($CompareSize))