Who will be the first to say that this would never have happened in a Boeing, and that the 747 never had a first engine failure?
I believe 747's maiden commercial flight had an engine problem.
The decision to fly back to Paris is not a simple coin toss hastily taken decision. I believe the Capt, after judging that it's not a "Mayday" issue, must have called Maintrol to ask them on suggestions and after assessing the situation and roping in FOCC, must have made the decision to land in Paris, based on financial and logistical reasons. If the captain, at any point in time, felt that safety of the a/c was in danger(land ASAP), he would have landed at the nearest alternative, no questions asked. Remember, the company can only give him suggestions, not command him. Capt takes the final decision.
If an IFSD happened on a twin, the decision to land would have been taken in milli-seconds after relight fails.
For us knowledgable in aircrafts, we know that losing an engine in a 4 holer is not an issue and the aircraft can continue the journey with the remaining engines. But to the general public, losing an engine on any aircraft is a catastrophe. Can you imagine the public repercussion if they knew that SQ flew an aircraft with one engine down for 10 hours. SQ image would have been tarnished.