Example:

JKCompare-ADGroupMemeber -Group1 GROUPNAME1 -Group2 GROUPNAME2

Optional Parameter:

-IncludeEqual yes

#13.11.2018 Jeremias Kühnis

Function JKCompare-ADGroupMemeber{
[CmdletBinding()]
Param(
    [Parameter(Mandatory=$true)]
    [string]$Group1,
    
    [Parameter(Mandatory=$true)]
    [string]$Group2,

    [Parameter(Mandatory=$false)]
    [ValidateSet("yes", "no")]
    [string]$IncludeEqual
)

IF($IncludeEqual -eq "Yes"){
    diff (Get-ADGroupMember $Group1) (Get-ADGroupMember $Group2) -Property 'SamAccountName' -IncludeEqual
}Else{
    diff (Get-ADGroupMember $Group1) (Get-ADGroupMember $Group2) -Property 'SamAccountName'
}

Write-Host "#############################################" -ForegroundColor Cyan
Write-Host "== This user is in both groups (If option is enabled)."
Write-Host "=> This user is in the second group ($group2)."
Write-Host "<= This user is in the first group ($group1)."
Write-Host "#############################################" -ForegroundColor Cyan
}