FADEC failure 135  

I'd imagine for most of us at sea level or even a little higher giving up the extra HP and doing a normal OEI is fine.  I'd think there are combinations of weight/density altitude and also availability of good places to slide an aircraft on where you would want to have the extra horsepower from the non fadec control engine to allow a hovering landing or very close to it.  Good instruction and practice makes it a non event but there have been people who on older twist grip styles toasted/overpseed the manual engine.