A useful thread outlining the decision process that one should go through when an in-flight emergency occurs.
The question of "nearest suitable airport" I think, all things considered, is a matter of time.
If you have two airports with equal weather and facilities then the one that is closer is probably the most suitable. However if your at 30,000' and that airfield is 60nms away then inevitably one would have to hold or take extended vectors.
The airport that is further away may turn out to be more "suitable" after all.
Flying any longer than is necessary with an engine that is shut-down or damaged is in my opinion irresponsible.