In your personal opinion would you prefer, as a pax on the NCL flight, to land at PIK or MME?
Passengers would prefer to land as close to their intended destination as possible.
That is why, when there is
enough prior notice that a flight will be diverted, both the airline and new airport can prepare for the arriving aircraft. In the case of EK diverts to PIK, Emirates sent staff to PIK, and PIK received additional border control and ground staff from GLA, in order to meet the aircraft immediately on arrival.
However, when there is
no prior notice that a flight will be diverted, it is better to divert to an airport where the airline already has a presence. In the case of the EK divert to NCL whereby the aircraft made several failed landing attempts at GLA, it would not have made sense to divert to PIK as neither Emirates nor PIK would have been prepared to handle the aircraft immediately upon arrival. It would have taken several hours to notify and transport staff and equipment from GLA to PIK. Passengers would have spent hours on the ground with no Emirates representatives. Diverting to NCL meant that the aircraft was met immediately upon arrival by the appropriate ground crew and EK staff required.