As much as ARM is associated with efficiency, the instruction set itself is largely irrelevant to the performance of modern CPUs. x86s CPUs are translating x86

As much as ARM is associated with efficiency, the instruction set itself is largely irrelevant to the performance of modern CPUs. x86s CPUs are translating x86 instructions into the CPU's native instruction set, and while that used to impose some non-trivial overhead, it's been trivial for quite some time.