@kolla
It makes a huge difference in what security you actually get. SSL/TLS only secures the transport. On the server, between external servers(!) and on your local HDD the message is not encrypted in any way. Nor can any manipulation be detected. For email, SSL/TLS can only provide (end-to-end) security in a closed or at least well-known environment. (And btw SSL and TLS are different things even if a user can neglect the difference. A developer/IT supporter can't.)
S/MIME encrypts the message, then you can transport it safely any which way you want without worrying about eavesdropping or manipulation and only the intended sender can decrypt it.
Makes hell of a difference for me. If I want to ensure confidential end-to-end communication I use S/MIME. If I want to secure login/account or traffic details in an insecure environment (esp. public hotspots, insecure wireless in general, untrusted LANs) I use SSL or TLS.
And stop kidding me about OSI's dead. It sure is but without the layered architecture the internet wouldn't be possible. We'd be stuck with 10base5 and there'd be no DSL or Wi-Fi at all. And probably you don't want to tell me that a hub, a switch or a router are exactly the same, do you?