I think its just that it works better for most applications, where you run them multiple times. JIT is going to be slower under emulation anyway. Also note that

I think its just that it works better for most applications, where you run them multiple times. JIT is going to be slower under emulation anyway. Also note that Rosetta uses the native libraries where available, so as soon as you call into say graphics libraries that is running native, not emulating. (I believe most of the relevant patents just expired; they don't emulate the vector instructions that are newer).