PS > (measure-command { .\RunspaceInstanceTest.ps1 }).TotalSeconds

RunspaceInstanceTest.ps1 file script:
class Writer
{
    static WriteLineS([string] $Msg)
    {
        for ($i=0; $i -lt 10; $i++)
        {
            [Console]::WriteLine("Static: Loop $i - $Msg")
            Start-Sleep -MilliSeconds 100
        }
    }

    WriteLineI([string] $msg)
    {
        for ($i=0; $i -lt 10; $i++)
        {
            [Console]::WriteLine("Instance: Loop $i - $Msg")
            Start-Sleep -MilliSeconds 100
        }
    }
}

$script = @'
    param ([object] $writerInstance, [string] $Title)

    class Writer
    {
        static WriteLineS([string] $Msg)
        {
            for ($i=0; $i -lt 10; $i++)
            {
                [Console]::WriteLine("Static: Loop $i - $Msg")
                Start-Sleep -MilliSeconds 100
            }
        }

        WriteLineI([string] $msg)
        {
            for ($i=0; $i -lt 10; $i++)
            {
                [Console]::WriteLine("Instance: Loop $i - $Msg")
                Start-Sleep -MilliSeconds 100
            }
        }
    }

    # Create new instance
    #$writerInstance = [Writer]::new()

    # Instance write
    $writerInstance.WriteLineI("$Title")

    # Static write
    #[Writer]::WriteLineS("$Title")
'@

$writer = [Writer]::new()

$rsp = [runspacefactory]::CreateRunspacePool(1, 10, $host)
$rsp.Open()

class Task
{
    [powershell] $powershell
    [System.IAsyncResult] $Async
}

$tasks = @()

1..5 | foreach {

    $task = [Task]::new()
    $tasks += $task

    $task.powershell = [powershell]::Create()
    $task.powershell.RunspacePool = $rsp
    $task.Async = $task.powershell.AddScript($script).AddArgument($writer).AddArgument("Task $_").BeginInvoke()
}

foreach ($task in $tasks)
{
    $task.powershell.EndInvoke($task.Async)
    $task.powershell.Dispose()
}

$rsp.Dispose()