raise vs Async.Raise

gistfile1.fs

type Microsoft.FSharp.Control.Async with
    static member Raise (e : #exn) = Async.FromContinuations(fun (_,econt,_) -> econt e)

#time
for i in [|1..1000000|] do
    try
        raise <| new System.Exception()
    with ex -> ()

async {
    for i in [|1..1000000|] do
        try
            return! Async.Raise <| new System.Exception()
        with ex -> ()
} |> Async.RunSynchronously