[adrian_b]

Their main architectural choice was not about "RISC" or "ARM" but it was choosing "Brainiac" over "Speed Demon", i.e. setting the goal to execute a great number of instructions per clock cycle at a moderate clock frequency, instead of executing a moderate number of instructions per clock cycle at a high clock frequency (the latter variant results in lower fabrication costs, which is why other companies were reluctant to pursue the same choice as Apple).

A high IPC is much easier to achieve when the instructions have a fixed-length encoding, so this RISC principle followed from their main choice.

[rbanffy]

ARM was chosen for the Newton, then the iPods, then the iPhone and so on. Apple’s experience with ARM has a long history. Same applies to RISC. Apple didn’t leave PPC because it was a dead-end. They went with Intel because IBM was not interested in developing a low power PPC just for Apple. IBM wasn’t (and still isn’t) even interested in developing a POWER chip for desktop workstations. If there are POWER machines that can be turned into workstations, it’s a side effect of them being targeted at entry-level half-rack systems.