I run twin tanks/ batteries etc.totally separate units.
Even with 1 tank I'd assume if you got bad fuel you would stop nor far from the harbour. Highly unlikely youd make it 100km out before issues arose.
Lots of things can go wrong with a motor, bad starter is common, solenoid, fuses, sensors etc.
The benefit of todays motors is often you get limp mode and not a total failure. Also linking your motor via nmea2000 gives you all the info you need on whats going wrong generally. Aswell as code flashes on display units. Not just a beep with old school motors.
Sat phone is a good option if your going wide regardless of 1 motor or 2.
Its totally a personal preference, one isn't better than another overall.
Like wives, having two is good for some or a nightmare for others