MailboxProcessor只是复制IOobservable吗

我想处理到消息的类型

Add x使程序记住数字x

Print使其打印所有记忆的数字

我为什么要写这个：

open System
type Message =
    | Add of int
    | Print
let mailbox = new MailboxProcessor<Message>(fun inbox -> 
        let rec loop history = async{
            let! msg=inbox.Receive()
            match msg with
                | Add x -> return! loop(history + x.ToString()+" ")
                | Print ->
                    printfn "%s" history
                    return! loop(history)
        }
        loop ""
    )
[<EntryPoint>]
let main argv = 
    mailbox.Start()
    mailbox.Post(Add 12)
    mailbox.Post(Add 56)
    mailbox.Post(Print)
    mailbox.Post(Add 34)
    mailbox.Post(Print)
    ignore <| Console.ReadLine()
    0

而不是这个：

open System
open System.Reactive.Subjects
type Message =
    | Add of int
    | Print
let subject = new Subject<Message>() 
[<EntryPoint>]
let main argv = 
    subject
        |> Observable.scan(fun history msg -> 
                match msg with
                        | Add x -> history + x.ToString()+" "
                        | Print ->
                            printfn "%s" history
                            history
            ) ""
        |> Observable.subscribe(fun _->())
        |> ignore
    subject.OnNext(Add 12)
    subject.OnNext(Add 56)
    subject.OnNext(Print)
    subject.OnNext(Add 34)
    subject.OnNext(Print)
    ignore <| Console.ReadLine()
    0

MailboxProcessor增加了额外的复杂性。我需要一个状态机，它获取一个状态并返回一个状态。但它迫使我使用inbox，它用于接收状态。

它对IObservable有什么好处吗？