[duskwuff]

I can't speak for Windows Phone, but iOS displays messages from iMessages -- their private messaging service -- almost identically to normal SMS. (There are some subtle indicators of which one's being used, but it's not obviously different.)

[Pxtl]

Oddly, the "official" messaging system baked into WinPHone 7 was actually Facebook messages. It didn't switch-over between FB and SMS messages silently, but it did intertwingle the messaging thread between the two platforms and there was a toggle to select which you were using to contact them.

Dunno what they do in WP8.