Unless the cause is fuel contamination, what are the odds of a second engine failing on the same flight? Almost zip. So as long as the aircraft can clear terrain with the remaining engine not above max continuous power, the case for proceeding to a good distant airport trumps a return to a marginal airport.
Max continuous means what it says - a good engine will run at that power setting all day if necessary. Often pilots are conditioned to forget that fact by certain instructors who want us to 'baby' their engines.
On the other hand, if there is evidence of fuel contamination (fluctuating fuel flow, rough running etc), or the remaining engine is showing signs of stress (like overheating as opposed to just sounding a bit louder than what you are accustomed to), it's a no- brainer - put it down asap.