Triple engine failure; which would you choose to keep left?
Using the inner engines allows you to maneuver easier as the yaw moment is smaller in comparison to the outboard engine which also means you need less rudder inputs to keep the course. The big advantage of needing less rudder to keep a straight path of flight is that you can react better because the rudder can move a bit more.

Which sides engine to use is depending on the wind situation (I would use the engine on the side the wind is coming from as you can turn into the wind better to keep your course) and other influences like if you need to turn left or right more often; avoid turning into a dead engine as Terry already mentioned).