Different like … totally. SMS was part of the very early GSM design work in the mid ‘80s and is built into the network at a fundamental level (this is why the

Different like … totally. SMS was part of the very early GSM design work in the mid ‘80s and is built into the network at a fundamental level (this is why the particular character limit etc etc)- it was designed in the GSM/SS7/ telco world and has been used for over thirty years. iMessage was designed and built by Apple as a single operator with virtually total control of the backend and user devices. They achieve similar results in completely different ways, the best analogy I can think of is how octopus’s and jellyfish can see too, but evolved eyes very different to our own.