If you're trying to enter the field I would highly suggest ARM. Mobile malware is the wild west and they really need analysts and hire a bunch of people with no

If you're trying to enter the field I would highly suggest ARM. Mobile malware is the wild west and they really need analysts and hire a bunch of people with no experience out of college. X86/64 is alot harder to enter the field in since theres alot more saturation so the barrier to entry is higher.